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Tue Jul 28, 2026 (1405/5/6)

	Jul 28 1405/5/6	14:00	Tuning self-interacting dark matter from dark kinetic heating in neutron stars Show Abstract Abstract:Compact astrophysical objects such as neutron stars (NS) offer a complementary probe for low DM-nucleon cross-sections. At these values DM self-interactions have been argued to play a non-negligible role. In the optically thin limit, we explore the capture and accumulation of asymmetric DM resulting from DM self-interactions. We demonstrate that self-interacting DM (SIDM) enhances the DM capture rate, which subsequently imparts observable changes to the NS thermal evolution, due to kinetic heating. The resulting late-time effect can sustain NS surface temperatures of ~ 1000-1200 K, a faint signature potentially detectable by advanced infrared observatories including the JWST, TMT, and ELT. Observing such a cold NS will establish upper bounds on the specific SIDM cross-section more stringent than those derived from the Bullet Cluster. Lecturer(s): Sambo Sarkar From : Jeonbuk National University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Wed Jul 22, 2026 (1405/4/31)

	Jul 22 1405/4/31	09:30	The 20 GeV Fermi halo: evidence for dark matter annihilation? Show Abstract Abstract:Fifteen years of the Fermi Large Area Telescope (LAT) data in the halo region of the Milky Way (MW) are analyzed to search for gamma rays from dark matter annihilation. Gamma-ray maps within the region of interest (\|l\| < 60 deg, 10 deg < \|b\| < 60 deg) are modeled using known components plus a halo-like component. A statistically significant halo-like excess is found with a spectral peak around 20 GeV, and examination of the fit residual maps indicates that a spherically symmetric halo component fits the map data well. The radial profile agrees with annihilation by the smooth NFW density profile. Various systematic uncertainties are investigated, but the 20 GeV peak remains significant. The halo excess spectrum can be fitted by annihilation with a particle mass m Ã¢?Â¼ 0.5-0.8 TeV and cross section Ã¢?Â¼ (5-8) x10^{-25} cm3 s^-1 for the bb channel. This cross section is larger than the upper limits from dwarf galaxies and the canonical thermal relic value, but considering various uncertainties, especially the density profile of the MW halo, the dark matter interpretation of the 20 GeV "Fermi halo" remains feasible. The prospects for verification through future observations are briefly discussed. Lecturer(s): Tomonori Totani From : University of Tokyo Research Group: HEPCO Group Weekly Seminar More Info. : Video
Sat Jul 18, 2026 (1405/4/27)

	Jul 18 1405/4/27	18:00	The Revolution in Reporting: How AI is transforming the study of nature Show Abstract Abstract:Since the invention of writing, our understanding of nature has been built upon reports. Tracing the evolution of scientific reporting offers a unique lens through which to view the evolution of physics itself. Today, with the rise of Large Language Models (LLMs), we stand in the midst of a revolution that is more than a technological shift. From the passive recording of observations to computational objects that can actively drive discovery, we are witnessing a transformation in the way we study nature. In this talk, I will explore how Artificial Intelligence (AI) is reshaping the practice of empirical sciences in its modern form and show that the next generation of experiments will undergo fundamental change. One manifestation of this transformation is the emergence of Foundation Models and self-supervised learning, in which AI systems learn structured representations directly from raw observations, rather than relying on human annotation. This shift changes not only how data are collected, presented, and analyzed, but also how observations are interpreted and transformed into knowledge. As an example, I will present Masked AutoEncoder (MAE) techniques applied to particle physics experiments, demonstrating how self-supervised learning can extract meaningful patterns without relying on extensive labeled datasets. I will then extend these concepts to cosmological observations from the Euclid mission, where similar architectures reveal latent representations. Lecturer(s): Saeed Ansarifard From : School of Physics, IPM Research Group: Physics Colloquium More Info. : Link
Tue Jul 14, 2026 (1405/4/23)

	Jul 14 1405/4/23	14:00	From Analogue Black Holes to Dilaton Gravity: Towards an Action-Based Description of Emergent Spacetimes Show Abstract Abstract:Simplified models have long played a central role in high-energy physics, providing valuable insight into phenomena that are otherwise mathematically intractable or experimentally inaccessible. In gravitational physics, processes such as Hawking radiation and superradiance remain extremely challenging to observe directly. Analogue gravity offers an alternative approach by realizing effective curved spacetimes in laboratory systems-including flowing fluids, Bose-Einstein condensates, and optical media-where key aspects of black hole physics can be investigated experimentally. Despite their success, analogue gravity models are typically formulated at the level of effective metrics and equations of motion, rather than arising from a generally covariant gravitational action. This raises a natural theoretical question: can these analogue spacetimes be described within a fundamental gravitational framework? In this seminar, I will present an action-based description of two-dimensional analogue black holes using dilaton gravity. Specifically, I will address the following questions: Which classes of dilaton gravity models reproduce the analogue black hole geometries realized in laboratory systems, and what physical assumptions characterize these models? I will show that these requirements place strong constraints on the admissible dilaton theories, thereby establishing a direct connection between experimental analogue gravity and the theoretical framework of two-dimensional dilaton gravity. Lecturer(s): Mohaddese Shams Nejati From : Institute for Advanced Studies in Basic Sciences Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Jun 30, 2026 (1405/4/9)

	Jun 30 1405/4/9	14:00	Fermion Zero Modes and Fermion Number 1/2 of the Electroweak Sphaleron Show Abstract Abstract:In this talk, I will discuss fermion bound states in the background of the electroweak SU(2) sphaleron for various values of the gauge coupling constant ($g$), the Higgs self-coupling constant ($\lambda$), and the Yukawa coupling constant ($y_q$). Numerical solutions of the coupled differential equations reveal the existence of a single fermion zero mode, whose presence can also be understood analytically. I will show how the sphaleron profile functions and the zero-mode wave functions become increasingly localized as $g$ and $\lambda$ increase, while the right-handed component of the zero mode decreases with $g$, but grows with the Yukawa coupling $y_q$. I will also discuss how the zero mode in the limit $g\to0$ differs from the solution in the pure Higgs background, highlighting the nonlinear and nonperturbative nature of the system. Finally, I will present a proof of the spectral mirror symmetry of the fermion spectrum and explain how, together with the existence of the zero mode, it implies that the electroweak sphaleron carries fermion number 1/2. Lecturer(s): Poupak Mogaddam From : Shahid Beheshti University Research Group: HEPCo Weekly Seminar More Info. : Link
Tue Jun 16, 2026 (1405/3/26)

	Jun 16 1405/3/26	14:00	Composite Asymmetric Dark Matter from Primordial Black Holes Show Abstract Abstract:We investigate a cogenesis scenario for composite asymmetric dark matter framework: a dark sector has a similar strong dynamics to quantum chromodynamics in the standard model, and the dark-sector counterpart of baryons is the dark matter candidate. The Hawking evaporation of primordial black holes plays the role of a source of heavy scalar particles whose CP-violating decay into quarks and dark quarks provides particle--anti-particle asymmetries in baryons and dark matter, respectively. Primordial black holes should evaporate after the electroweak phase transition and before the big-bang nucleosynthesis for explaining the baryon asymmetry of the Universe and for consistent cosmology. We find that this scenario explains the observed values for both baryon and dark matter energy densities when the heavy scalar particles have a mass of $10^6$-- $10^9$ GeV and the primordial black holes have masses of $10^7$â??$10^9$ g. Lecturer(s): Takumi Kuwahara From : Jilin University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Jun 09, 2026 (1405/3/19)

	Jun 09 1405/3/19	14:24	Optical signatures of Einsteinâ??Eulerâ??Heisenberg AdS/dS black holes in the light of the Event Horizon Telescope Show Abstract Abstract:Recent observations of the supermassive black holes M87* and Sgr A* by the Event Horizon Telescope (EHT) have opened a new window into testing gravity and fundamental physics in the strong-field regime. Inspired by this progress, this talk presents a comprehensive study of the optical appearance of black holes in Einsteinâ??Eulerâ??Heisenberg (EEH) theory, extended to include a cosmological constant (AdS/dS). Due to non-linear electrodynamics (NLE) effects inherent to this theory, photons do not follow the background metric but instead propagate along null geodesics of an effective geometry. I will first derive this effective metric for the EEH-AdS/dS black hole. Subsequently, I will analyze the resulting null geodesic structure, compute the black hole shadow's geometrical shape and size, and determine the energy emission rate and light deflection angle. Finally, I will confront our theoretical predictions with the EHT data for M87, establishing lower bounds on the shadow radius and discussing how EEH parameters modify the image we expect to observe. Lecturer(s):* Khadije Jafarzade From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Jun 02, 2026 (1405/3/12)

	Jun 02 1405/3/12	14:00	Nonsymmetric Degenerate GR and Cosmology: A Candidate for Two Problems Regularization of Singularities and Inflation Show Abstract Abstract:Einstein's General Relativity, despite its remarkable successes, suffers from several fundamental shortcomings, including the presence of spacetime singularities and its silence on the early universe. Numerous attempts have been made to resolve these issues, yet none have proven fully satisfactory. Regularization of singularities often requires the introduction of exotic matter, while inflation is typically driven by an artificial scalar field with fine-tuned potentials. In this talk, we present an alternative approach that may serve as a candidate to address both problems simultaneously. Our work is rooted in Einstein's later dream: a nonsymmetric generalization of General Relativity. Einstein spent the last three decades of his life attempting to construct such a theory, primarily with the goal of unifying gravity and electromagnetism. The central question was: how can one relax the symmetry condition g_{\mu\nu} = g_{\nu\mu} and formulate a consistent theory of gravity based on a nonsymmetric metric G_{\mu\nu}? Any second-rank tensor G_{\mu\nu} can be uniquely decomposed into its symmetric and antisymmetric parts: G_{\mu\nu} = g_{\mu\nu} + \omega_{\mu\nu}, g_{\mu\nu} = g_{\nu\mu}, \omega_{\mu\nu} = -\omega_{\nu\mu}. The challenge is to understand how the addition of the antisymmetric part \omega_{\mu\nu} modifies the geometric structure of General Relativity. This problem is far from trivial. Despite efforts by Einstein, SchrÃ¶dinger, Moffat, and others, a fully consistent and physically viable nonsymmetric GR has remained elusive. The mathematical and physical difficulties are substantial, and even prominent figures such as Witten have avoided entering this complex territory. The theory is often described as a maze, where at every turn one faces multiple choices, and only a carefully navigated path leads to a consistent framework. In this talk, we introduce a new attempt to construct a consistent nonsymmetric General Relativity. We then apply this formalism to two of the most pressing problems in gravitational physics and cosmology: the regularization of spacetime singularities and the origin of cosmic inflation. Our results suggest that the antisymmetric part \omega_{\mu\nu} can naturally tame singularities without exotic matter and can drive a geometric phase of inflation without the need for an artificial scalar field. We present explicit solutions, asymptotic analyses, and physical interpretations, and discuss the prospects of this program as a unified framework for gravitational phenomena. Lecturer(s): Seyed Ebrahim Akrami Sanzigh From : Semnan University Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue May 26, 2026 (1405/3/5)

	May 26 1405/3/5	14:00	Gravity-assisted neutrino masses Show Abstract Abstract:Gravity is generally expected to violate global symmetries, including lepton number. However, neutrino masses from the Planck-suppressed Weinberg operator are typically too small to account for oscillation data. We propose a new model-building approach to low-scale neutrino mass generation, in which an intermediate spontaneous symmetry-breaking scale generates masses and mixings in the heavy neutral lepton (HNL) sector, while leaving an unbroken residual symmetry G_res that forbids light-neutrino masses. The observed light-neutrino masses then arise because gravity breaks G_res via Planck-suppressed operators, inducing the small lepton-number violation required in low-scale seesaw constructions. The HNLs form pseudo-Dirac pairs, with masses potentially within reach of future colliders and complementary tests in precision searches such as charged lepton flavour violation (cLFV). As an illustration, we present a representative realisation of this class of models and show that, for O(1) operator coefficients, it predicts a region in the (MR, theta)-plane that can be testable via displaced-vertex searches at the High-Luminosity (HL-)LHC and the FCC-ee. Lecturer(s): Salvador Centelles Chulia From : University of Valencia Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue May 19, 2026 (1405/2/29)

	May 19 1405/2/29	14:00	Exploring Latent Representations of the Data Space for Highly Motivated Subdominant Signals Show Abstract Abstract:This talk presents two frameworks for the investigation of new physics. It begins with a discussion of the traditional approach using the likelihood ratio test before introducing a novel framework that leverages latent space representations. This second approach aims to isolate highly motivated, subdominant signals within complex datasets. By employing self-supervised learning models, such as Masked Autoencoders, the original data is projected smoothly onto a manifold. The central hypothesis is that within this learned latent space, the underlying structure of subdominant signals becomes more distinct and separable from dominant features, enabling their robust detection and subsequent analysis. Lecturer(s): Saeed Ansarifard From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
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