BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Contributory: Quintom dark energy: Future attractor and phantom cr ossing in light of DESI DR2 observations DTSTART;VALUE=DATE-TIME:20261120T053000Z DTEND;VALUE=DATE-TIME:20261120T054500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1077@indico.narit.or.th DESCRIPTION:Speakers: Phusuda Thanankullaphong (Centre for Theoretical Phy sics and Natural Philosophy\, Mahidol University)\nWe study the late-time cosmological dynamics of a two-field dark-energy model consisting of a can onical quintessence scalar field and a phantom scalar field in a spatially flat Friedmann-Lemaître-Robertson-Walker universe. The fields are minima lly coupled to gravity and uncoupled at the level of the potential\, with the quintessence sector governed by an exponential potential and the phant om sector by an inverse power-law potential. By reformulating the backgrou nd equations as a five-dimensional autonomous dynamical system\, we identi fy and analyze the fixed points and their stability properties\, revealing stable late-time attractors corresponding to phantom-dominated accelerate d expansion. We confront the model with observations through a Bayesian pa rameter estimation performed using the cobaya framework\, employing severa l combinations of recent cosmological datasets\, including Pantheon+ super novae\, compressed cosmic microwave background distance priors\, DESI DR2 baryon acoustic oscillation measurements\, and DES year-5 supernova data. The observational constraints favor a dynamical dark-energy sector moderat ely and are consistent with deviations from a cosmological constant at the present epoch. The regions of parameter space preferred by the data are c ompatible with the stable accelerating solutions identified in the dynamic al analysis\, establishing a direct connection between phase-space stabili ty and observational viability. A notable feature of the model is that the effective dark-energy equation of state undergoes phantom divide crossing in a gradual and asymptotic manner\, rather than as a sharp transition.\n \nhttps://indico.narit.or.th/event/234/contributions/1077/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1077/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Avik De: The Non-Metricity Gravity Approach DTSTART;VALUE=DATE-TIME:20261120T040000Z DTEND;VALUE=DATE-TIME:20261120T050000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1064@indico.narit.or.th DESCRIPTION:General Relativity formulates gravitation through spacetime cu rvature using the Levi-Civita connection\, which assumes both vanishing to rsion and zero non-metricity. However\, alternative geometric descriptions exist within the Geometric Trinity of Gravity. Among these\, Non-Metricit y Gravity\, specifically \\(f(Q)\\) gravity and its scalar-tensor extensio ns\, attributes gravitational interactions strictly to the non-metricity t ensor\, setting curvature and torsion tensors to zero while introducing co upled scalar fields to unlock rich\, dynamical behaviors.\n\nA crucial fea ture that makes modified non-metricity theories particularly intriguing is that the affine connection is no longer uniquely fixed by the metric tens or alone. In isotropic and homogeneous spacetimes\, such as the FLRW unive rse\, the requirement of zero curvature and zero torsion yields three dist inct classes of affine connections. Similarly\, applying these geometric c onstraints to static spherically symmetric systems reveals two independent classes of connections.\n\nThese non-trivial connection classes transform the study of non-metricity gravity from a simple metric modification into a deep structural probe of spacetime geometry. Depending on which connect ion branch is realized\, the underlying non-metricity scalar \\(Q\\) acqui res completely different dynamic expressions. This mathematical degree of freedom allows identical spatial metrics to yield dramatically different f ield equations\, influencing late-time cosmic acceleration\, inflationary dynamics\, and black hole or stellar solutions. This work highlights how e xploring these distinct connection choices opens up compelling new pathway s for understanding fundamental gravity.\n\nhttps://indico.narit.or.th/eve nt/234/contributions/1064/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1064/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Atsushi Naruko: Understanding Cosmological Perturbatio ns through the Separate-Universe Approach DTSTART;VALUE=DATE-TIME:20261119T060000Z DTEND;VALUE=DATE-TIME:20261119T070000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1074@indico.narit.or.th DESCRIPTION:How much can we learn about an inhomogeneous universe from hom ogeneous background solutions? The separate-universe approach offers a rem arkably simple way to address this question: on sufficiently large scales\ , different regions of the universe can be treated approximately as homoge neous universes\, allowing us to follow the nonlinear evolution of cosmolo gical perturbations without solving the full inhomogeneous equations.\n\nI n this talk\, I will introduce the basic physical picture of the separate- universe approach and its formulation in terms of the spatial gradient exp ansion. I will then explain how this leads to the δN formalism\, which re lates large-scale curvature perturbations to differences in the local expa nsion history. I will also discuss the assumptions underlying this descrip tion\, why it works\, and where its limitations become important. Finally\ , I will briefly touch upon extensions of the standard framework and recen t developments in the study of nonlinear cosmological perturbations. The a im is to provide an accessible overview of the subject\, emphasizing physi cal intuition and its usefulness for understanding the early universe.\n\n https://indico.narit.or.th/event/234/contributions/1074/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1074/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Masashi Kimura: Black Hole Quasinormal Modes and the N on-Uniqueness of Effective Potentials DTSTART;VALUE=DATE-TIME:20261119T040000Z DTEND;VALUE=DATE-TIME:20261119T050000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1073@indico.narit.or.th DESCRIPTION:Quasinormal modes (QNMs) describe the characteristic oscillati ons of black holes and play an important role in observations of the ringd own phase. These modes are determined by the effective potential in the ma ster equation for gravitational perturbations\, raising the question of to what extent the potential can be uniquely determined from the QNM spectru m. In this talk\, we explore this question using Darboux transformations o f the wave function. We examine under what conditions Darboux transformati ons yield physically reasonable effective potentials. We also discuss the implications of these transformations for interpreting black hole QNM spec tra.\n\nhttps://indico.narit.or.th/event/234/contributions/1073/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1073/ END:VEVENT BEGIN:VEVENT SUMMARY:Online Plenary — Kent Yagi: Gravitational-Wave Tests of String-I nspired Gravity DTSTART;VALUE=DATE-TIME:20261119T023000Z DTEND;VALUE=DATE-TIME:20261119T033000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1072@indico.narit.or.th DESCRIPTION:Gravitational waves provide a unique window into the strong-fi eld regime of gravity\, offering unprecedented opportunities to test gener al relativity and search for signatures of new physics. In this talk\, I w ill focus on Einstein-dilaton-Gauss-Bonnet gravity\, a quadratic modificat ion of general relativity motivated by string theory. I will first discuss the post-Newtonian corrections that arise during the inspiral phase of co mpact binary coalescences and review current observational constraints obt ained from inspiral signals. I will then describe how black hole ringdown frequencies are modified in this theory and the corresponding constraints from ringdown observations. Accurately modeling the merger phase requires numerical relativity simulations\, which are computationally expensive and time-consuming. To address this challenge\, I will present new approaches for constructing inspiral-merger-ringdown waveforms in Einstein-dilaton-G auss-Bonnet gravity more efficiently\, paving the way for stronger tests o f string-inspired modifications to gravity with current and future gravita tional-wave observations.\n\nhttps://indico.narit.or.th/event/234/contribu tions/1072/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1072/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Ryo Saito: Probing the Early Universe with Gravitation al-Wave Background Anisotropies: Universal Structures at Large Angles DTSTART;VALUE=DATE-TIME:20261118T040000Z DTEND;VALUE=DATE-TIME:20261118T050000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1071@indico.narit.or.th DESCRIPTION:The stochastic gravitational-wave background (SGWB) offers a n ew window onto the early Universe. While its sky-averaged spectrum is the primary target of current searches\, distinct primordial and astrophysical mechanisms can produce similar spectra over a finite observational band. Angular anisotropies provide complementary information that may help ident ify the origin of a signal.\n\nThe importance of such information is famil iar from the cosmic microwave background (CMB). In particular\, large-angl e CMB anisotropies trace primordial perturbations that were superhorizon a t recombination and therefore provide a relatively direct window into infl ationary initial conditions. SGWB anisotropies may offer a similar probe\, potentially retaining information from epochs far earlier than recombinat ion. At the same time\, important differences exist between CMB and SGWB o bservations. I will discuss how these similarities and differences determi ne which angular information can be extracted from SGWB observables and ho w it should be interpreted.\n\nTo organize primordial SGWB anisotropies\, I will introduce the Cosmological Form Factor (CFF)\, a model-independent framework describing their response to cosmological long-wavelength pertur bations. The CFF characterizes how long modes modulate local short-scale G W statistics and connects observable anisotropies to cosmological correlat ion functions. This connection allows general principles\, including stati stical isotropy and locality\, to determine the angular and polarization s tructures\, while amplitudes\, frequency dependence\, and source-time depe ndence retain information about the underlying mechanism. Both propagation and fossil effects arise as representative realizations of this common fr amework. As an application\, I will show that nearly scale-invariant scala r long modes yield a universal Sachs–Wolfe-like large-angle scaling.\n\n https://indico.narit.or.th/event/234/contributions/1071/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1071/ END:VEVENT BEGIN:VEVENT SUMMARY:Online Plenary — Elisa G. M. Ferreira: Probing the Particle Phys ics of Ultralight Dark Matter: From Galaxies to the Solar System DTSTART;VALUE=DATE-TIME:20261117T060000Z DTEND;VALUE=DATE-TIME:20261117T070000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1068@indico.narit.or.th DESCRIPTION:Small-scale astrophysical observations provide a powerful wind ow into the particle physics properties of dark matter. In this talk\, I w ill focus on ultralight dark matter and discuss how its distinctive predic tions for different astrophysical systems can be used to constrain the par ticle mass. I will highlight the current observational bounds and the assu mptions and systematic uncertainties affecting their interpretation. I wil l also discuss how these observations can provide information about other fundamental properties of ultralight bosons\, including their spin\, self- interactions\, and fractional abundance. Finally\, I will discuss how our own Solar System can provide new ways to probe the particle physics proper ties of ultralight dark matter.\n\nhttps://indico.narit.or.th/event/234/co ntributions/1068/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1068/ END:VEVENT BEGIN:VEVENT SUMMARY:Online Plenary — Eleonora Di Valentino: Cracks in the Standard C osmological Model: Tensions\, Robustness\, and Hints of New Physics DTSTART;VALUE=DATE-TIME:20261116T093000Z DTEND;VALUE=DATE-TIME:20261116T103000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1065@indico.narit.or.th DESCRIPTION:The ΛCDM model has been extraordinarily successful in describ ing the Universe\, but increasingly precise observations are beginning to expose cracks in this remarkably simple picture. The Hubble constant discr epancy remains the most striking example\, while recent measurements of th e expansion and growth histories of the Universe\, together with cosmologi cal constraints on neutrino masses\, are adding new pieces to the puzzle. But which of these tensions are robust\, and which depend on our choice of datasets\, methodology\, or cosmological assumptions? In this talk\, I wi ll examine the evidence behind the main cosmological tensions and ask what remains when these choices are varied. I will then explore whether the su rviving discrepancies can be accommodated by extensions of the standard mo del\, including dynamical dark energy\, new early-Universe physics\, and i nteractions in the dark sector. The emerging picture may not yet tell us w hat lies beyond ΛCDM\, but it is beginning to tell us where (and how) we should look.\n\nhttps://indico.narit.or.th/event/234/contributions/1065/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1065/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Antonio De Felice: From Data to Dynamics: A Simple Pha ntom-Crossing Dark Energy Parametrization DTSTART;VALUE=DATE-TIME:20261116T040000Z DTEND;VALUE=DATE-TIME:20261116T050000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1063@indico.narit.or.th DESCRIPTION:Is the time dependence of dark energy genuinely complicated\, or can current observations be described by a much simpler expression?\n\n I will present a data-driven approach to this question within VCDM\, a min imally modified theory of gravity that allows a consistent treatment of co smological perturbations even when the effective dark-energy equation of s tate crosses the phantom divide.\n\nWe begin by reconstructing the dark-en ergy equation of state using Bayesian splines constrained by cosmic microw ave background\, baryon acoustic oscillation\, and Type Ia supernova obser vations. The reconstruction favors relatively smooth histories\, while Bay esian evidence does not justify introducing excessive functional complexit y. We then employ exhaustive symbolic regression to identify compact and i nterpretable analytic expressions compatible with the reconstructed evolut ion.\n\nA particularly interesting outcome is the one-parameter form \\(w( a) = w_0/\\sqrt{a}\\)\, which provides a competitive fit compared with con ventional two-parameter parametrizations\, including CPL.\n\nIts simplicit y leads to concrete predictions: the phantom-crossing redshift is determin ed by the single parameter \\(w_0\\)\, the effective dark-energy density i s suppressed at early times\, and the phantom phase is transient\, avoidin g a future big-rip singularity.\n\nI will discuss the observational implic ations of this result and explain how the underlying VCDM dynamics can acc ommodate phantom crossing without introducing an additional propagating sc alar degree of freedom.\n\nhttps://indico.narit.or.th/event/234/contributi ons/1063/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1063/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Shinji Tsujikawa: Dark Energy with Stable Phantom-Divi de Crossing: Model Construction and Observational Constraints DTSTART;VALUE=DATE-TIME:20261116T023000Z DTEND;VALUE=DATE-TIME:20261116T033000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1062@indico.narit.or.th DESCRIPTION:Recent cosmological observations have revived interest in dark energy whose equation of state evolves from below -1 to above -1 at low r edshift. In this talk\, I will discuss how to construct theoretically cons istent models realizing this transition and test them against observations . I will first explain the obstacles to achieving such a crossing in shift -symmetric Horndeski and generalized Proca theories with luminal gravitati onal-wave propagation and no direct dark-matter couplings. I will then pre sent two ways to overcome these obstacles: introducing a scalar potential that breaks shift symmetry in a Horndeski model\, and combining a generali zed Proca vector field with a canonical scalar field. Particular attention will be paid to the conditions ensuring the absence of ghost and gradient instabilities\, as well as the implications for matter clustering and gra vitational lensing. I will also present constraints on a scalar-vector-ten sor dark-energy model using the DES five-year supernova sample\, second-re lease DESI baryon acoustic oscillation measurements\, compressed cosmic mi crowave background constraints\, and growth data from redshift-space disto rtions. The results allow stable crossing histories and improve the best-f it likelihood relative to flat ΛCDM. I will discuss Bayesian model compar ison\, including its sensitivity to theoretical viability conditions and p rior normalization\, and the prospects for distinguishing these models thr ough cosmic expansion and structure growth.\n\nhttps://indico.narit.or.th/ event/234/contributions/1062/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1062/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Nature of the dark matter distribution near the Gala ctic Center black hole: Insights from stellar orbital precession DTSTART;VALUE=DATE-TIME:20261120T051500Z DTEND;VALUE=DATE-TIME:20261120T053000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-951@indico.narit.or.th DESCRIPTION:Speakers: Debojit Paul (Department of Physics\, Gauhati Univer sity)\n**Abstract:**\nThe stellar orbits near the Galactic Center black ho le provide a unique probe for understanding the nature of mass distributio n as well as carrying out tests of gravity. Inferring the nature of mass d istribution in the region is crucial for understanding the formation histo ry of the black hole and how it interacts with its environment. In this wo rk we consider several viable dark matter models and constrain the paramet ers of the models which are consistent with the latest bound on dark mass near the Galactic Center. The pericenter shift of stellar orbits in presen ce of such mass distributions are worked out. We compare the dark matter p recession with general relativistic precession and identify regions where dark matter induced effects might be dominant. We consider 13 S-stars that have passed or expected to pass their pericenter within the next decade. The prospect of detection of the dark matter effects in these stellar orbi ts through existing and upcoming large telescopes have been explored. In t he orbit of S2\, the effect of the different dark matter profiles along wi th some modified gravity models is investigated. It is seen that the orbit of S2 is insensitive to dark matter distribution but provides a good prob e for testing modified gravity theories. Additionally\, other stellar orbi ts with low eccentricity and large semi-major axis are found to be promine nt probes for distinguishing different dark matter distributions. We ident ify five S-star orbits that can be used to distinguish between these mass profiles using observational facilities like Keck\, Very Large Telescope a nd upcoming Thirty Meter Telescope.\n\n\n----------\nReferences:\n\n 1. Pa ul D.\, Kalita S.\, 2026\, [MNRAS][1]\, 547\, 2 \n 2. GRAVITY Collaboratio n et al.\, 2024\, [A&A][2]\, 692\, A242\n\n\n [1]: https://academic.oup.c om/mnras/article/547/2/stag318/8483897\n [2]: https://www.aanda.org/artic les/aa/full_html/2024/12/aa52274-24/aa52274-24.html\n\nhttps://indico.nari t.or.th/event/234/contributions/951/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/951/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: Late-Time Dynamics in Accelerating Nonlinear f (T ) Gr avity via Hybrid Scale Factor : Bayesian Analysis and Cosmological implica tions DTSTART;VALUE=DATE-TIME:20261119T081000Z DTEND;VALUE=DATE-TIME:20261119T081200Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-962@indico.narit.or.th DESCRIPTION:Speakers: Pratik P. Ray (Vellore Institute of Technology-AP Un iversity)\nThis study offers a comprehensive reconstruction of modified Te leparallel (f(T)) gravity model with three distinct non-linear as well as novel forms employing a hybrid scale factor to depict the expansion histor y of the universe. We investigate a physically motivated cosmological para metrization through this hybrid scale factor that can explain a smooth tra nsition from an early decelerated epoch to the present accelerated evoluti on. This scale factor is then used to derive the corresponding model param eters. These parameters are rigorously constrained using the Monte Carlo M arkov Chain (MCMC) analysis with the help of Bayesian statistics and incor porating late-time observations from Hubble\, Baryon Acoustic Oscillations (BAO) and Patheon+SH0ES datasets. The investigation of dynamical paramete rs such as the equation of state parameter and cosmological parameters ind icates alignment with an accelerated expansion phase in both the present a nd late time epochs. Validation is conducted by assessing the energy condi tions\, verifying the feasibility of the model forms with particular empha sis on the violation of the strong energy condition that indicates dark en ergy dominance in modified gravity scenarios. This investigation has been instrumental in determining models that remain consistent with cosmologica l observations and theoretical requirements. The reconstructed forms of th e model effectively mimic ΛCDM at late times\, providing significant insi ghts into possible extensions of general relativity and bolstering f(T) gr avity theory as a robust explanation for cosmic acceleration.\n\nhttps://i ndico.narit.or.th/event/234/contributions/962/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/962/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: Beyond ΛCDM: Probing Structure Growth and Observation al Viability of Generalized f (Q\, Lm) Gravity DTSTART;VALUE=DATE-TIME:20261119T080800Z DTEND;VALUE=DATE-TIME:20261119T081000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-959@indico.narit.or.th DESCRIPTION:Speakers: RAJ KUMAR DAS (Physics And Applied Mathematics Unit \,Indian Statistical Instiute Kolkata)\n$f(Q\, \\mathcal{L}_m)$ gravity i s a well-known extension of $f(Q)$ gravity\, obtained through non-minimal or additive minimal coupling in the action's Lagrangian density. Existing literature within the framework of $f(Q\, \\mathcal{L}_m)$ has explored th e cosmographic scenario through various approaches\, including background- level analyses and comparisons with $\\Lambda$CDM (Myrzakulov et al.\, Phy s.\\ Lett.\\ B 139506\, 2025\; Hazarika et al.\, Physics of the Dark Unive rse 50\, 102092\, 2025). In this work\, we investigate the additive minima l coupling in a generalized power-law form\, $f(Q\,\\mathcal{L}_m) = -Q^\\ mu + \\alpha \\mathcal{L}_m^{\\\,\\nu} + \\beta$\, where $\\mu$\, $\\nu$\, $\\alpha$\, and $\\beta$ are the extra degrees of freedom introduced by t he model. We derive the key cosmological evolution equation\, the Hubble f unction $H(z)$\, by adopting a suitable novel parametrization. A distincti ve feature of this theoretical framework is the non-conservation of the ma tter sector (a non-conserved continuity equation)\, which we highlight and study under the condition $\\nu \\neq 1$\; this non-conservation is signi ficant\, as it effectively mimics a particle creation scenario. We constra in the model's free and extra parameters\, and examine their effects on th e cosmographic scenario\, using Observational Hubble Data (OHD)\, Baryon A coustic Oscillation (BAO) measurements from DESI DR2\, and three Type Ia S upernovae (SNe Ia) catalogs (Pantheon+\, Union3\, and the Dark Energy Surv ey). Since our framework inherently involves non-conservation\, we extend the analysis beyond the background level to the perturbative regime\, deri ving the perturbed field equations of $f(Q\,\\mathcal{L}_m)$ together with the perturbed Euler and continuity equations\, and study the growth of st ructure and the impact of the non-conservation term on the growth equation \, further performing a joint observational analysis incorporating the $f\ \sigma_8$ probe. To statistically assess our results\, we performed a Baye sian evidence analysis\, treating $\\Lambda$CDM as the reference model\; b ased on this analysis\, our non-conservative model shows a statistical edg e over $\\Lambda$CDM in several cases\, depending on the dataset combinati on used. These results position non-conservative $f(Q\,\\mathcal{L}_m)$ gr avity as a physically motivated and observationally testable alternative t o $\\Lambda$CDM\, rooted in an effective particle-creation mechanism.\n\nh ttps://indico.narit.or.th/event/234/contributions/959/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/959/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: A Potential Black Hole Mimicker From Curvature-Matter Coupled Theory of Gravity DTSTART;VALUE=DATE-TIME:20261119T080400Z DTEND;VALUE=DATE-TIME:20261119T080600Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-960@indico.narit.or.th DESCRIPTION:Speakers: Debanjan Debnath (Indian Institute of Technology Kan pur)\nI wish to give a presentation\, in which I will talk about a clas s of horizonless\, regular ultra-compact objects which may arise in a theo ry of gravity where fluid variables may couple to the curvature scalar of the spacetime. This kind of non-minimal interaction between fluid variable s and the Ricci scalar generates a vacuum-like equation of state in the in terior\, while the exterior remains exactly Schwarzschild. The interior an d exterior spacetimes are glued through a infinitesimally thin-shell at th e boundary of the spacetimes. The interior metric is regular everywhere an d the shell has given a stiff-matter equation of state\, and near-horizon compactness can potentially mimic black-hole phenomenology without a event horizon. Unlike the Mazur-Mottola gravastar and its variants\, the presen t model predicts a typical ultra-compact mass-radius window\, with masses in the range $1.4-2.1M_\\odot$ and radii in the range $5-7$ km. In additio n\, this framework also predicts a unique geometric-thermodynamic shell te mperature in the ultra-compact limit distinctly different from the Hawking temperature.\n\nhttps://indico.narit.or.th/event/234/contributions/960/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/960/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: Phantom divide crossing with interacting scalar fields DTSTART;VALUE=DATE-TIME:20261119T080200Z DTEND;VALUE=DATE-TIME:20261119T080400Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-957@indico.narit.or.th DESCRIPTION:Speakers: Akshara S B (VELLORE INSTITUTE OF TECHNOLOGY\, VELLO RE)\nThe accelerated expansion of the Universe poses a serious challenge t o our understanding about the dark sector\, motivating the investigation o f dark matter and dark energy within a unified framework. In this work\, w e deal with the analysis of two-interacting scalar field model inspired by the hybrid inflation potential. We initially perform the cosmographic rec onstruction of the Hubble parameter utilising a modified parametrisation w hich is constrained by the Bayesian Markov Chain Monte Carlo (MCMC) method . The cosmographic parameters are estimated using the Observational Hubble Data\, Baryon Acoustic Oscillation\, Type Ia Supernovae\, Cosmic Microwav e Background\, Cosmic Chronometers and Dark Energy Spectroscopic Instrumen t data. The reconstructed Hubble parameter is used as an input to numerica lly solve the coupled scalar field equations\, analysing the evolution of the interacting scalar fields. The reconstructed scalar field dynamics are then utilised to explore the dark energy equation of state. Further\, the evolution of deceleration\, jerk and snap parameters are also studied to understand the cosmological aspects of the model. This work demonstrates a cosmographic approach in connecting the observational constraints with in teracting scalar field dynamics\, paving a way for understanding the unifi ed dark energy models.\n\nhttps://indico.narit.or.th/event/234/contributio ns/957/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/957/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: f(R) gravity scalarons near black hole horizon DTSTART;VALUE=DATE-TIME:20261119T070000Z DTEND;VALUE=DATE-TIME:20261119T071500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-988@indico.narit.or.th DESCRIPTION:Speakers: Pranjali Bhattacharjee (Gauhati University)\nThe Gal actic Center (GC) black hole Sgr A* gives us an opportunity to perform hor izon scale tests of black hole physics and deviations from General Relativ ity\, thanks to observations carried out by the Event Horizon Telescope (E HT). In this work we study the impact of the scalar degree of freedom (sca laron) of f(R) gravity theory on the size and shape of GC black hole by us ing a recently developed stationary\, axisymmetric and vacuum metric of f( R) theory. We encounter a minimum bound of $10^{-17}$ eV for the scalaron mass using 1σ upper bound on the deviation parameter produced by EHT-Keck and EHT-VLT measurements. Lighter scalarons increase the shadow size beyo nd that measured by the EHT. The displacement and asymmetry in the shape o f the black hole shadow are employed to test the no-hair theorem and it is observed that $10^{-16}$ eV scalarons yield the exact Kerr like shadow an d a $6\\%$ departure from the Kerr quadrupole. We infer preservation of th e no-hair theorem for such scalaron mass and further examine the possibili ty of violation of the theorem. The same mass scale reproduces the PPN par ameter $\\gamma$ constrained in the weak field limit of the solar system. This is for the first time we report a convergence of horizon scale test a nd solar system test of f(R) gravity by using the scalaron mass. The prosp ect of constraining the scalaron mass using gravitational waves is an exci ting avenue to be highlighted.\n\nhttps://indico.narit.or.th/event/234/con tributions/988/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/988/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: The Ringdown and the Tide: Fingerprints of Dark Matt er Halo Profiles DTSTART;VALUE=DATE-TIME:20261117T100000Z DTEND;VALUE=DATE-TIME:20261117T101500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-948@indico.narit.or.th DESCRIPTION:Speakers: Avijit Chowdhury (Indian Institute of Astrophysics)\ nAstrophysical black holes are expected to reside in environments enriched by dark matter\, raising the possibility that environmental effects may l eave observable imprints on gravitational-wave signals. We investigate how the structure of a surrounding dark-matter halo modifies both the ringdow n and tidal response of a static\, spherically symmetric black hole. The h alo is modelled using a generalized $(\\alpha\,\\beta\,\\gamma)$ density p rofile within the Einstein cluster framework. We compute the quasinormal m ode spectrum and static axial tidal Love numbers\, and examine their depen dence on the halo compactness and density profile. We show that the halo i nduces a characteristic redshift of the quasinormal frequencies and dampin g rates\, with the strongest influence arising from the inner halo structu re. Time-domain evolutions confirm the frequency-domain results and exhibi t late-time tails whose behaviour is governed by the outer density profile . We further demonstrate that the tidal Love number probes the halo throug h a different radial weighting than the ringdown spectrum\, making the two observables complementary. Our results suggest that combining ringdown an d tidal measurements can help constrain the spatial distribution of dark m atter around black holes and distinguish environmental effects from genuin e deviations of the vacuum black-hole geometry.\n\nhttps://indico.narit.or .th/event/234/contributions/948/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/948/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Non-Trivial Cosmology from Fractal Spacetime\, Memor y Effects\, and Modified Gravity DTSTART;VALUE=DATE-TIME:20261117T093000Z DTEND;VALUE=DATE-TIME:20261117T094500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-953@indico.narit.or.th DESCRIPTION:Speakers: Aarav Shah ()\nThe success of the $\\Lambda$CDM mode l and General Relativity has established the standard paradigm of modern c osmology\, yet the fundamental nature of spacetime remains an open questio n. This talk explores three complementary directions for extending the geo metric foundations of modern cosmology. I first consider inflation in a fr actal spacetime\, where non-integer spatial dimensions modify the inflatio nary dynamics and the Mukhanov–Sasaki equation through an effective mome ntum $k_{\\rm{eff}}$\, leading to corrections in the scalar power spectrum and spectral index $n_s$. Confronting the Starobinsky model with Planck 2 018 observations constrains the effective dimension to the range $D \\appr ox [2.7\,3]$\, while fractal corrections render Natural Inflation phenomen ologically viable with sub-Planckian axion decay constants. I then extend the semiclassical Wheeler-DeWitt framework by incorporating a causal non-M arkovian memory\, leading to an effective non-integer temporal dimension t hat introduces an additional contribution to the primordial power spectrum with a $k^{3/4}$ scaling\, enhancing high-$\\ell$ CMB temperature anisotr opies and producing scale-dependent modifications of primordial non-Gaussi anity. Finally\, I present a De Donder-Weyl formulation of Einstein-Cartan cosmology\, where torsion generalizes the underlying spacetime geometry\, yielding torsion-modified Friedmann equations and demonstrating the limit ations of conventional power-law cosmological solutions. Together\, these studies investigate the cosmological consequences of extending spacetime t hrough non-integer spatial and temporal dimensions and torsion\, providing new perspectives on physics beyond the standard cosmological paradigm.\n\ nhttps://indico.narit.or.th/event/234/contributions/953/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/953/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Inflationary trispectrum of gauge fields from scalar and tensor exchanges DTSTART;VALUE=DATE-TIME:20261117T091500Z DTEND;VALUE=DATE-TIME:20261117T093000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-983@indico.narit.or.th DESCRIPTION:Speakers: Jishnu Sai Puthiyedath (Ewha Womans University\, Seo ul)\nIn this paper\, we compute the inflationary trispectrum of primordial gauge fields generated through the scalar and tensor exchanges in models with spectator U(1) gauge fields which are kinetically coupled to the infl aton. Focusing on the connected four-point autocorrelation function of gau ge fields\, we derive exact analytical expressions for the full trispectru m of both electric and magnetic fields using the in-in formalism and cosmo logical diagrammatic rules\, and explore their respective contributions in specific momentum configurations. For the scalar exchange\, we find that the trispectrum signal in the equisided configuration grows with the excha nge momentum and reaches its maximum in the flattened limit. However\, in the counter collinear limit\, we show that the non-linearity parameter ass ociated with the trispectrum scales quadratically with the corresponding p arameter of the cross-correlation bispectrum of magnetic fields and curvat ure perturbations\, thereby establishing a hierarchical relation between t he higher- and lower-order correlation functions. For the tensor exchange\ , the trispectrum displays a richer angular dependence\, reflecting the se nsitivity to the orientation of the momentum quadrilateral with respect to the tensor polarisation\, producing characteristic angular modulations in the trispectrum. Detecting such angular signatures in future high-precisi on cosmological observations would provide a novel window into tensor-medi ated interactions in the early universe.\n\nhttps://indico.narit.or.th/eve nt/234/contributions/983/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/983/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: From CPL to Canonical Fields: Constraining Quintesse nce with the Tomographic AP Test DTSTART;VALUE=DATE-TIME:20261116T061500Z DTEND;VALUE=DATE-TIME:20261116T063000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-946@indico.narit.or.th DESCRIPTION:Speakers: Zahra Davari (Korea Institute for Advanced Study (KI AS))\nThe nature of dark energy remains one of the central open questions in cosmology. While observational analyses commonly constrain phenomenolog ical equation-of-state parametrizations such as the Chevallier–Polarski –Linder (CPL) model\, theoretical interpretations require translating th ese constraints into physically motivated scalar-field models.\n\nWe prese nt a computational framework that directly maps observational likelihoods in the $(\\Omega_m\,w_0\,w_a)$ parameter space onto the parameter spaces o f canonical quintessence potentials without recomputing the full observati onal likelihood. The method employs likelihood-guided mapping based on the tomographic Alcock–Paczyński test combined with Type Ia supernova and baryon acoustic oscillation observations. For each potential\, we solve th e scalar-field background evolution numerically and determine an effective CPL representation over the observed redshift range\, allowing observatio nal constraints to be projected efficiently onto the underlying theoretica l parameters.\n\nWe apply this approach to exponential\, pseudo–Nambu– Goldstone boson (PNGB)\, and inverse power-law (IPL) quintessence models. The resulting constraints reveal that viable scalar-field models occupy on ly a narrow region of the effective CPL parameter space\, considerably sma ller than the full phenomenological CPL posterior. This demonstrates how t heoretical consistency substantially reduces the allowed dark-energy param eter space and provides a practical route for confronting fundamental dark -energy models with current and future cosmological observations.\n\nhttps ://indico.narit.or.th/event/234/contributions/946/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/946/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: JWST-informed Cosmological Inference from 21-cm Tomo graphy DTSTART;VALUE=DATE-TIME:20261117T070000Z DTEND;VALUE=DATE-TIME:20261117T071500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-981@indico.narit.or.th DESCRIPTION:Speakers: Madhurima Choudhury (Birla Institute of Technology a nd Science\, Pilani - Hyderabad campus.)\nThe redshifted 21-cm line of neu tral hydrogen provides a unique probe of the high-redshift Universe\, trac ing the evolving state of the intergalactic medium (IGM) during the Epoch of Reionization (EoR). The 21-cm signal\, however\, depends on both the un derlying cosmological density field and the astrophysical properties of th e sources driving reionization\, leading to potentially strong degeneracie s between cosmological and astrophysical parameters. This degeneracy prese nts a fundamental challenge for extracting robust cosmological information from 21-cm observations alone. Observations of high-redshift galaxies wit h the James Webb Space Telescope (JWST) provide complementary information on the population of sources responsible for ionizing the IGM. In this wor k\, we investigate a JWST-informed framework for extracting cosmological i nformation from 21-cm tomography. We construct simulated EoR lightcones sp anning a joint parameter space of cosmological and astrophysical parameter s and generate corresponding galaxy observables\, including UV luminosity functions\, together with the 21-cm signal. We first use the JWST-like gal axy observables to constrain the properties of the underlying galaxy popul ation and use these constraints as informative priors on the astrophysical parameters entering the 21-cm forward model. We then employ machine-learn ing-based inference to recover cosmological parameters from the 21-cm fiel d while marginalizing over the remaining astrophysical uncertainties. By c omparing 21-cm-only and JWST-informed inference\, we quantify how external information on the high-redshift galaxy population changes the cosmologic al posterior and the associated astrophysics–cosmology degeneracies.\n\n https://indico.narit.or.th/event/234/contributions/981/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/981/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Background and Perturbation Constraints on Spinor Fi eld Dark Energy from Recent Cosmological Observations DTSTART;VALUE=DATE-TIME:20261116T070000Z DTEND;VALUE=DATE-TIME:20261116T071500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-975@indico.narit.or.th DESCRIPTION:Speakers: Mahendra Goray (Dept. of Physics\, S.P College\, Sid o Kanhu Murmu University\, Dumka\, Jharkhand)\nWe investigate a nonlinear self-interacting spinor field as a dynamical dark-energy candidate capable of driving the late-time accelerated expansion of the Universe. The model is formulated within a spatially flat Friedmann–Lemaître–Robertson –Walker framework\, where the spinor field is minimally coupled to gravi ty and generates an effective dark-energy equation of state through its se lf-interaction potential. We study both the background and perturbation dy namics of the model\, deriving the evolution of the Hubble parameter (H(z) )\, equation-of-state parameter (w(z))\, deceleration parameter (q(z))\, a nd the growth of matter density perturbations. The background parameters a re constrained through a Markov Chain Monte Carlo (MCMC) analysis using re cent observational datasets\, including cosmic chronometers\, Pantheon sup ernovae\, and baryon acoustic oscillation measurements. To assess the impa ct on structure formation\, we implement the model at the perturbation lev el and examine its predictions for the growth rate ($f\\sigma_8$(z))\, mat ter power spectrum\, and the evolution of density fluctuations. We find th at the spinor dark-energy scenario successfully reproduces the observed ex pansion history while remaining compatible with current large-scale struct ure measurements. The effective equation of state evolves dynamically and approaches the cosmological-constant limit at late times\, while allowing mild deviations at intermediate redshifts. Statistical model comparison sh ows that the spinor-field framework provides a viable and competitive alte rnative to the standard $\\Lambda$CDM cosmology\, motivating further inves tigation with forthcoming high-precision surveys such as DESI\, Euclid\, a nd Rubin Observatory.\n\nhttps://indico.narit.or.th/event/234/contribution s/975/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/975/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Observational constraints on Fractional Holographic Da rk Energy in $f(T)$ gravity DTSTART;VALUE=DATE-TIME:20261116T080800Z DTEND;VALUE=DATE-TIME:20261116T081000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-969@indico.narit.or.th DESCRIPTION:Speakers: Chingkheinganba Meetei Elangbam (National Institute of Technology\, Manipur\, Imphal\, India)\nWe explore the cosmological imp lications of Fractional Holographic Dark Energy within the context of $f(T )=\\beta(-T)^n$ gravity\, in which the Hubble parameter is determined impl icitly. The model incorporates fractional corrections through a generalize d entropy-area relation\, allowing for the inclusion of nonlocal effects i n the dark energy sector. The model parameters are optimized using Hubble parameter measurements\, DES supernova data 5 year\, and BAO observations for DESI DR2 via a MCMC analysis. Our results show that the model remains consistent with current observational data and provides a viable cosmologi cal scenario. The dynamical analysis indicates that the model maintains a positive energy density and a negative pressure throughout the cosmic evol ution\, ensuring physical consistency. The equation of state parameters ex hibit a quintessence-like behavior at the present epoch and gradually evol ve toward a cosmological constant-like phase at late times. The decelerati on parameter confirms a transition from deceleration to acceleration at a redshift $z_t \\approx 0.78$. Furthermore\, the statefinder diagnostic rev eals noticeable deviations from the $\\Lambda$CDM model at intermediate re dshifts\, while approaching the standard fixed point $\\{r\,s\\} = \\{1\,0 \\}$ in the asymptotic future. The estimated age of the Universe is also f ound to be consistent with observational constraints. Overall\, the FHDE m odel within $f(T)$ gravity provides a physically consistent and observatio nally viable description of late-time cosmic acceleration\, and may serve as a promising alternative to the standard $\\Lambda$CDM paradigm.\n\nhttp s://indico.narit.or.th/event/234/contributions/969/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/969/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Modified Chaplygin gas with recent observations in f(Q \,B) gravity DTSTART;VALUE=DATE-TIME:20261116T080200Z DTEND;VALUE=DATE-TIME:20261116T080400Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-974@indico.narit.or.th DESCRIPTION:Speakers: Dr. Sanasam Surendra Singh (NIT MANIPUR)\nIn this wo rk\, we explore the cosmological dynamics of a modified gravity framework based on the function $f(Q\,B)=\\delta Q^{2}+\\beta B$\, where $Q$ denotes the nonmetricity scalar and $B$ is the boundary term that relates $Q$ to the Ricci scalar. The matter sector is modeled using the Modified Chaplygi n Gas (MCG) with the equation of state $p=A\\rho-\\frac{D_{1}}{\\rho^{\\al pha}}$\, allowing the model to interpolate between early-time matter behav ior and late-time cosmic acceleration. By deriving an analytical expressio n for the Hubble parameter $H(z)$\, we perform a parameter estimation usin g Markov Chain Monte Carlo (MCMC) techniques in conjunction with the lates t cosmological observations: $46$ Hubble parameter measurements\, $15$ BAO data points\, DESI DR2 BAO data and the Pantheon+ Type Ia supernovae comp ilation. The best-fit values are obtained as $H_0=72.2814^{+3.4702}_{-4.52 09}$ km/s/Mpc\, $A_s = 0.6964^{+0.0779}_{-0.1258}$\, $\\alpha = 0.0027^{+0 .0225}_{-0.0209}$ and $A = 0.0024^{+0.0702}_{-0.0464}$. The deceleration p arameter transitions at redshift $z_{tr} \\approx 0.946$\, while the prese nt-day value is $q_0 = -0.789$. The model yields an age of the Universe $t _0 \\approx 13.53$ Gyr and a present EoS parameter $\\omega_0 \\approx -0. 691$\, which reflects the late-time acceleration consistent with observati onal bounds. These results demonstrate that the MCG scenario within $f(Q\, B)$ gravity provides a viable and observationally consistent framework for explaining the late-time accelerated expansion of the Universe.\n\nhttps: //indico.narit.or.th/event/234/contributions/974/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/974/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Geometry and Stability of Wormholes in Symmetric Telep arallel Gravity with Dark Energy and Rotation Profiles DTSTART;VALUE=DATE-TIME:20261116T080000Z DTEND;VALUE=DATE-TIME:20261116T080200Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-976@indico.narit.or.th DESCRIPTION:Speakers: Sourav NA (Central University of Haryana)\nThis work investigates wormhole geometries in the framework of symmetric teleparall el (f($\\mathcal{Q}$)) gravity by incorporating holographic and mixed dark energy density profiles. Exact wormhole solutions are obtained using rota tional velocity profiles to construct the redshift function and dark energ y density profiles to determine the shape function. For suitable parameter choices\, the solutions satisfy the flare-out condition and exhibit asymp totically well-behaved geometries. We further analyze the energy condition s\, with particular emphasis on the null energy condition (NEC) at the wor mhole throat\, and demonstrate that the coupling parameter ($\\gamma$) pla ys a significant role in governing NEC violation. In addition\, the physic al properties of the obtained wormholes are explored through the complexit y factor\, anisotropy\, exoticity\, and embedding diagrams\, highlighting the viability of these solutions in modified gravity.\n\nhttps://indico.na rit.or.th/event/234/contributions/976/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/976/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Classical Eikonal for Binary Black Hole Scattering i n Dark Matter Backgrounds DTSTART;VALUE=DATE-TIME:20261120T050000Z DTEND;VALUE=DATE-TIME:20261120T051500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-956@indico.narit.or.th DESCRIPTION:Speakers: Arpita Mitra (CTP NAS\, Mahidol University\, Nakhon Sawan campus)\nDespite significant advances in post-Minkowskian gravity\, scattering-amplitude methods\, and gravitational-wave modeling\, existing frameworks largely assume vacuum binary dynamics and do not systematically incorporate coherent environmental effects. We develop a unified Hamilton ian framework for compact binaries embedded in coherent ultralight dark ma tter\, combining post-Minkowskian gravity with Hamiltonian deformation the ory\, the classical interaction picture\, and the Magnus expansion. The re sulting eikonal captures dark matter–induced corrections to gravitationa l-wave observables\, providing a systematic framework and potential avenue for probing ultralight dark matter with gravitational-wave observations.\ n\nhttps://indico.narit.or.th/event/234/contributions/956/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/956/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Peera Simakachorn DTSTART;VALUE=DATE-TIME:20261120T023000Z DTEND;VALUE=DATE-TIME:20261120T033000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1076@indico.narit.or.th DESCRIPTION:https://indico.narit.or.th/event/234/contributions/1076/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1076/ END:VEVENT BEGIN:VEVENT SUMMARY:Online Plenary — Laura Iacconi: Primordial black holes from infl ation: on the decoupling between large and small scales DTSTART;VALUE=DATE-TIME:20261119T090000Z DTEND;VALUE=DATE-TIME:20261119T100000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1075@indico.narit.or.th DESCRIPTION:Primordial black holes can be produced from the collapse of la rge perturbations generated from inflation on scales much smaller than tho se seeding the large-scale structure formation.\n\nIt is possible that the large peak in scalar power at high wavenumbers might induce corrections t o the scalar power spectrum on large scales\, e.g. in the form of loop cor rections\, endangering the success of inflation in explaining the observed statistics of primordial perturbations.\n\nIn this talk\, I will give an update on recent debates on the viability of such inflationary scenarios.\ n\nI will demonstrate that the 1-loop correction to a large-scale adiabati c mode due to a band of enhanced short-scale perturbations decouples from all detailed properties of the peak\, including its maximum amplitude\, an d does not lead to an observable effect.\n\nhttps://indico.narit.or.th/eve nt/234/contributions/1075/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1075/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Homothetic Killing Horizons in Vaidya and Kerr–Vai dya Black Holes DTSTART;VALUE=DATE-TIME:20261119T071500Z DTEND;VALUE=DATE-TIME:20261119T073000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-985@indico.narit.or.th DESCRIPTION:Speakers: Ritwika Ghoshal (Indian Institute of Technology Kanp ur)\nI would like to give a presentation in which I will discuss the exist ence and physical implications of homothetic Killing vectors (HKVs) in a b road class of dynamical Vaidya spacetimes\, including generalized spherica lly symmetric Husain-type solutions and rotating Kerr–Vaidya geometries. By solving the conformal Killing equations\, it can be demonstrated that these spacetimes admit a unique class of HKVs only when the dynamical para meters\, namely the mass\, charge\, and rotation parameter\, evolve linear ly with the advanced null coordinate. For Kerr–Vaidya spacetimes\, the e xistence of an HKV requires both the mass and angular momentum to be dynam ical and satisfy a definite relation between their rates of evolution. The null hypersurface where the HKV becomes null defines a homothetic Killing horizon (HKH)\, providing a natural generalization of the Killing horizon for nonstationary black holes. The presence of an HKV allows the original dynamical spacetime to be conformally mapped to a stationary spacetime\, thereby enabling the application of standard geometric methods associated with Killing horizons. Using this framework\, we analyse the geometric and thermodynamic properties of HKHs by evaluating different notions of surfa ce gravity and identifying the conformally invariant surface gravity relev ant for dynamical black-hole thermodynamics. Finally\, a maximal analytic extension of a self-similar charged Vaidya spacetime is constructed the HK H framework provides a suitable setting for investigating the particle cre ation by Hawking radiation in dynamical backgrounds. These results establi sh homothetic symmetry as a powerful organizing principle for understandin g horizon geometry\, thermodynamics\, and quantum phenomena in a wide clas s of nonstationary black-hole spacetimes.\n\nhttps://indico.narit.or.th/ev ent/234/contributions/985/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/985/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — T.R. Govindarajan DTSTART;VALUE=DATE-TIME:20261118T023000Z DTEND;VALUE=DATE-TIME:20261118T033000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1070@indico.narit.or.th DESCRIPTION:https://indico.narit.or.th/event/234/contributions/1070/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1070/ END:VEVENT BEGIN:VEVENT SUMMARY:Online Plenary — Roy Maartens: Testing the Standard Model of Cos mology DTSTART;VALUE=DATE-TIME:20261117T080000Z DTEND;VALUE=DATE-TIME:20261117T090000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1069@indico.narit.or.th DESCRIPTION:The standard LCDM model of cosmology has been highly successfu l in fitting the data from numerous cosmological surveys. Nevertheless\, i t is always good physics to test the standard model. In addition\, various tensions are emerging in the data\, especially the Hubble tension\, which may indicate problems with the standard model. I will give an overview of the key features of the model that can be tested. Then I will give exampl es and updates on some of these tests.\n\nhttps://indico.narit.or.th/event /234/contributions/1069/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1069/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Takashi Hiramatsu: Cosmological Constraints on Extende d Theories of Gravity from CMB Observations DTSTART;VALUE=DATE-TIME:20261117T040000Z DTEND;VALUE=DATE-TIME:20261117T050000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1067@indico.narit.or.th DESCRIPTION:The late-time accelerated expansion of the Universe\, revealed by observations of Type Ia supernovae and other cosmological probes\, may be explained by extensions of general relativity. Various extended theori es of gravity have been proposed to explore gravitational physics beyond g eneral relativity. In this talk\, I will focus on constraining such theori es using observations of the cosmic microwave background (CMB). In particu lar\, I will consider degenerate higher-order scalar-tensor (DHOST) theori es\, generalised Proca theories\, and a model propagating only two tensor degrees of freedom. To investigate these theories\, we have developed a Bo ltzmann solver incorporating the effective field theory (EFT) approach to gravity. Using this solver\, we perform Markov chain Monte Carlo (MCMC) an alyses with the Planck 2018 likelihood to derive observational constraints on the EFT parameters characterising each model.\n\nhttps://indico.narit. or.th/event/234/contributions/1067/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1067/ END:VEVENT BEGIN:VEVENT SUMMARY:Plenary — Luis Ureña López DTSTART;VALUE=DATE-TIME:20261117T023000Z DTEND;VALUE=DATE-TIME:20261117T033000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-1066@indico.narit.or.th DESCRIPTION:https://indico.narit.or.th/event/234/contributions/1066/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/1066/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Kuchowicz gravastars in Horava gravity and Einstein-ae ther theory DTSTART;VALUE=DATE-TIME:20261116T080400Z DTEND;VALUE=DATE-TIME:20261116T080600Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-971@indico.narit.or.th DESCRIPTION:Speakers: Meghanil Sinha (National Institute of Technology Man ipur)\nThis work introduces a new gravastar model inspired by the Mazur-Mo ttola framework within Lorentz-violating gravity\, specifically Hořava gr avity and Einstein-aether theory with the help of Kuchowicz metric functio n. The proposed gravastar consists of three distinct regions: a de Sitter- like core\, a thin shell filled with ultra-relativistic matter\, and an ex terior vacuum spacetime. Exact solutions obtained for each region demonstr ate the consistency and viability of the model. A detailed investigation o f the shell's physical properties\, along with the other conditions confir ms its stability and physical plausibility. The resulting gravastar soluti ons are free from singularities and event horizons\, offering a compelling alternative to the conventional black hole paradigm in Lorentz-violating gravity theories.\n\nhttps://indico.narit.or.th/event/234/contributions/97 1/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/971/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: Chaotic scattering in binary black hole systems DTSTART;VALUE=DATE-TIME:20261119T080000Z DTEND;VALUE=DATE-TIME:20261119T080200Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-987@indico.narit.or.th DESCRIPTION:Speakers: Sampurna Bhar (Indian Institute of Technology\, Madr as)\nWhen we consider the the case of chaotic scattering in a region descr ibed by a potential or a massive object\, we see that the behavior of part icle trajectories are heavily dependent on initial conditions\, which even tually decide whether particles stay in the scattering region or exit it t hrough different exits. Initially\, the H\\'enon-Heiles potential is taken as a model to study these trajectories\, where we can find that a scaling relation exists between the fraction of particles trapped in the potentia l as function of relativistic parameter $\\beta$\, when each of these part icles are projected with a different set of initial conditions. We then tr y to investigate if similar scaling relations could be found for null geod esics propagating around a binary black hole system described by the Majum der-Papapetrou (MP) binary black hole solution. Our study can thus be able to demonstrate the use of nonlinear dynamics to find such an example of t he existence of scaling laws in gravitational systems.\n\nhttps://indico.n arit.or.th/event/234/contributions/987/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/987/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash talk: Dark Energy and Black Holes DTSTART;VALUE=DATE-TIME:20261119T080600Z DTEND;VALUE=DATE-TIME:20261119T080800Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-986@indico.narit.or.th DESCRIPTION:Speakers: Bisweswar Sen ()\nWe study aspects of black-hole spa cetimes in the presence of dark-energy components\, focusing on how the eq uation of state and associated curvature diagnostics constrain physically distinct regimes. Starting from the Schwarzschild geometry\, we derive the Kretschmann scalar as a coordinate-invariant measure of curvature and use it to characterize the behavior near the horizon and at the central singu larity. We then discuss how dark-energy motivated modifications can be inc orporated and how they affect invariant quantities and horizon structure. Our results provide a compact set of analytic expressions and checks that are useful for comparing different dark-energy/black-hole models.\n\nhttps ://indico.narit.or.th/event/234/contributions/986/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/986/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Can Gravity Take Us Beyond the Standard Picture of t he Universe? Cosmology in Extended Proca-Nuevo Gravity DTSTART;VALUE=DATE-TIME:20261116T060000Z DTEND;VALUE=DATE-TIME:20261116T061500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-984@indico.narit.or.th DESCRIPTION:Speakers: Kavya Nagarakodige Shashikantha (Universiti Malaya)\ nThe success of the ΛCDM model is tempered by unresolved questions surrou nding the nature of dark energy and the cosmological constant. These chall enges motivate the exploration of modified theories of gravity as viable a lternatives to General Relativity. In this talk\, I present the Extended P roca-Nuevo (EPN) framework\, a ghost-free vector–tensor theory in which a massive spin-1 field drives the late-time evolution of the Universe. I w ill discuss the background cosmology and its implications for possible asp ects of alleviating cosmological tensions. I will highlight recent observa tional constraints from current cosmological datasets\, demonstrating the potential of the EPN framework as a promising candidate for cosmology beyo nd the standard model.\n\nhttps://indico.narit.or.th/event/234/contributio ns/984/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/984/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: A unified framework to study $f$-family of modified gravity theories DTSTART;VALUE=DATE-TIME:20261116T063000Z DTEND;VALUE=DATE-TIME:20261116T064500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-980@indico.narit.or.th DESCRIPTION:Speakers: Saikat Chakraborty (Institute of Research and Develo pment\, Duy Tan University\, Vietnam)\nI will introduce a neat mathematica l framework that can be utilized to study\, in a unified manner\, differen t aspects of $f(R)\, f(T)\, f(G)$ or $f(Q)$ gravity. As an example of the application of this framework\, I will show it's applicability for a compa rative analysis between $f(R)$ gravity and the trivial FLRW connection bra nch of $f(Q)$ gravity\, with respect to the two following questions: (1) p rovide a purely cosmographic measure on the deviation from GR based on the current data and (2) the behaviour of the underlying theory (more precise ly\, of it's deviation from GR) given a certain cosmological evolution. Ti me permitting\, I will briefly introduce the direction of a further intere sting application of this framework.\n\nhttps://indico.narit.or.th/event/2 34/contributions/980/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/980/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Breaking the Taylor Barrier in Cosmology DTSTART;VALUE=DATE-TIME:20261116T064500Z DTEND;VALUE=DATE-TIME:20261116T070000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-977@indico.narit.or.th DESCRIPTION:Speakers: SAI SWAGAT MISHRA (BITS PILANI\, Hyderabad Campus)\n We present a unified analysis of the late-time cosmic expansion by bridgin g model-independent cosmography with modified gravity\, using the latest D ESI DR2 BAO data. A comparative study of Taylor\, Padé\, and Chebyshev ex pansions shows that while Taylor breaks down beyond low redshift\, Padé a pproximants\, especially (2\,1)\, deliver stable\, high-redshift reconstru ctions and are strongly preferred by information criteria\, closely tracki ng LCDM. Leveraging this\, we embed the Padé (2\,1) framework within f(T) gravity and contrast it with direct dynamical solutions of the modified F riedmann equations. A comprehensive MCMC analysis with DESI DR2 and comple mentary probes reveals remarkable agreement between the two approaches\, w ith both outperforming LCDM. Our results establish Padé cosmography as a powerful and reliable interface between data-driven reconstruction and fun damental gravity.\n\nhttps://indico.narit.or.th/event/234/contributions/97 7/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/977/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Fermion condensate at the event horizon DTSTART;VALUE=DATE-TIME:20261116T080600Z DTEND;VALUE=DATE-TIME:20261116T080800Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-970@indico.narit.or.th DESCRIPTION:Speakers: Vladimir Dzhunushaliev (al-Farabi KazNU)\nSome argum ents are considered in favor of the idea that the canonical anticommutatio n relations for fermions should be modified in curved spacetime near the e vent horizon of a black hole. Such a modification is expected to lead to a change in the source term of the inhomogeneous Dirac equation describing the two-point Green’s function. By introducing an {\\it ad hoc} source i nto the Dirac equation that mimics the modification of these anticommutati on relations\, stationary solutions are obtained and interpreted as two-po int Green’s functions of fermions located near the event horizon. Owing to their stationarity\, these Green’s functions describe a fermion conde nsate near the event horizon.\n\nhttps://indico.narit.or.th/event/234/cont ributions/970/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/970/ END:VEVENT BEGIN:VEVENT SUMMARY:Flash Talk: Probing Energy Flow in the Dark Sector with DESI DR2 DTSTART;VALUE=DATE-TIME:20261116T081000Z DTEND;VALUE=DATE-TIME:20261116T081200Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-968@indico.narit.or.th DESCRIPTION:Speakers: Vipin Kumar Sharma (Universty of Punjab\, Lovely Pro fessional University)\nWe investigate the possibility of energy exchange i n the dark sector for interacting dark energy models\, using the latest DE SI DR2 baryon acoustic oscillation measurements. Our finding suggest that current observations do not provide significant evidence for dark sector i nteractions\, but they allow the possibility of a weak energy flow that ca n be further tested with future high-precision cosmological surveys.\n\nht tps://indico.narit.or.th/event/234/contributions/968/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/968/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Dynamical analysis of Bianchi type-IX cosmology with a scalar field mediated dark sector interaction DTSTART;VALUE=DATE-TIME:20261116T071500Z DTEND;VALUE=DATE-TIME:20261116T073000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-964@indico.narit.or.th DESCRIPTION:Speakers: Ashmita . (Khon Kaen University)\nThe recent DESI DR 2 preference for a time-varying dark-energy equation of state\, together w ith the long-standing difficulty of explaining why an initially anisotropi c universe should evolve toward isotropy\, motivates the study of interact ing dark-sector models in anisotropic backgrounds. We investigate the dyna mics of Bianchi type-IX cosmologies containing pressureless dark matter co upled to dark energy in the form of a quintessence scalar field $\\phi$ wi th exponential potential $V(\\phi)=V_0\\\,e^{-\\lambda\\phi}$. Energy exch ange between the two dark components is mediated by the scalar field throu gh the interaction term $Q=\\kappa\\beta\\dot\\phi\\\,\\rho_{\\rm DM}$\, w here $\\kappa^2=8\\pi G$ and $\\beta$ is a dimensionless coupling. Because Bianchi-IX models generically recollapse\, the Hubble scalar $H$ vanishes at the moment of maximum expansion\, where the expansion-normalized varia bles of the standard Wainwright-Ellis formalism diverge. We therefore adop t the $D$-normalized phase-space formalism of Hewitt\, Uggla\, and Wainwri ght\, which compactifies the state space and remains regular through the r ecollapse\, including the moment of maximum expansion at which $H = 0$. To gether with the modified conservation equations for the two dark component s\, the Einstein Klein Gordon system reduces to a closed autonomous polyno mial dynamical system\, whose fixed points we classify by linear stability analysis\, supplemented by center-manifold theory for the non-hyperbolic points. The fixed points shows the kinetic-dominated\, coupling modified m atter dominated\, curvature scalar\, scalar field dominated and coupled sc aling families\; the last is the anisotropic analogue of the Amendola scal ing attractor. Restricting to the initially expanding\, isotropizing traje ctories\, we map the region of the $(\\lambda\,\\beta)$ plane in which ani sotropic Bianchi-IX models approach an accelerating Friedmann Robertson Wa lker state.\n\nhttps://indico.narit.or.th/event/234/contributions/964/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/964/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Model-Independent Evidence for a Localized Anomaly i n the Late-Time Expansion History DTSTART;VALUE=DATE-TIME:20261117T071500Z DTEND;VALUE=DATE-TIME:20261117T073000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-963@indico.narit.or.th DESCRIPTION:Speakers: Shibendu Gupta Choudhury (Indian Institute of Astrop hysics)\nIn this talk\, I present a model-independent spline reconstructio n of cosmological distances using latest low-redshift datasets to investig ate the late-time expansion history of the Universe. Comparing the reconst ructed expansion history with the prediction of the Planck $\\Lambda$CDM m odel\, I demonstrate a localized deviation over a certain redshift interva l which reaches a maximum significance of approximately 3.5$\\sigma$ near $z=0.47$. I further demonstrate that this feature persists under substanti al variations of the reconstruction methodology\, dataset composition and sound-horizon calibration. I argue using mock analyses that the reconstruc tion is unbiased and that the observed anomaly is unlikely to arise from r econstruction bias or miscalibrated uncertainties. If confirmed by future observations\, this localized feature could point to previously unrecogniz ed late-time physics or reveal subtle inconsistencies between early and la te Universe cosmological probes.\n\nhttps://indico.narit.or.th/event/234/c ontributions/963/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/963/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Testing Sub-Horizon Approximations in Interacting Da rk-Sector Cosmology DTSTART;VALUE=DATE-TIME:20261117T090000Z DTEND;VALUE=DATE-TIME:20261117T091500Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-961@indico.narit.or.th DESCRIPTION:Speakers: Priyanka Saha (IIT kanpur)\nSub-horizon and quasi-st atic approximations are widely employed in cosmological simulations to eff iciently model the evolution of perturbations in theories beyond $\\Lambda $CDM. However\, their validity can depend on the underlying dark-sector ph ysics and the scales being considered. In this work\, we investigate these approximations in an interacting scalar-field dark-sector model\, where d ark matter and dark energy are coupled. We derive the full linear perturba tion equations and obtain their sub-horizon and quasi-static limits\, allo wing a direct comparison between the approximate and full dynamics. We stu dy the resulting evolution of matter perturbations and compare the interac ting model with $\\Lambda$CDM and a non-interacting scalar-field scenario. This provides a systematic assessment of when the approximations accurate ly capture the underlying perturbation dynamics and how dark-sector intera ctions can modify their validity. Our results are relevant for interpretin g and improving the treatment of interacting dark-sector models in cosmolo gical simulations and large-scale-structure studies.\n\nhttps://indico.nar it.or.th/event/234/contributions/961/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/961/ END:VEVENT BEGIN:VEVENT SUMMARY:Contributory: Aspects of Spontaneous Symmetry Breaking in Cosmolog y DTSTART;VALUE=DATE-TIME:20261117T094500Z DTEND;VALUE=DATE-TIME:20261117T100000Z DTSTAMP;VALUE=DATE-TIME:20261026T141319Z UID:indico-contribution-234-955@indico.narit.or.th DESCRIPTION:Speakers: Malavika K (Vellore Institute of Technology)\nWe exp lore if a late-time cosmic acceleration and a mild variation of fundamenta l constants can be accommodated within a common scalar-tensor framework. T he fundamental constants we focus on are the Newtonian gravitational coupl ing $G$ and the electron mass $m_e$. The scalar-tensor framework under con sideration is a generalized Brans-Dicke theory with an additional matter f ield. The viability of this framework is explored in the context of well-e stablished late-time cosmic expansion history\, namely\, a standard $\\Lam bda$CDM expansion and an extended $\\Lambda$CDM expansion (where a rationa l (Pad\\'e-like) deformation is considered). We reconstruct and show that the resulting effective potential of the matter field naturally develops a Higgs-like symmetry-breaking structure with a redshift-dependent mass ter m\, leading to a mild evolution of the vacuum expectation value. This vari ation leads to an evolution of proton-to-electron mass ratio $\\mu$ which is compared with observational bounds derived from quasar absorption spect ra. We find that in order to accommodate a reasonably mild variation of $\ \mu$\, the Brans-Dicke scalar field must behave as a chameleon.\n\nhttps:/ /indico.narit.or.th/event/234/contributions/955/ LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel URL:https://indico.narit.or.th/event/234/contributions/955/ END:VEVENT END:VCALENDAR