SCHOOL OF PHYSICS :: Seminars

Seminars

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Tue Nov 18, 2025 (1404/8/27)

	Nov 18 1404/8/27	14:00	Gravitational Wave Signature and the Nature of Neutrino Masses: Majorana, Dirac, or Pseudo-Dirac? Show Abstract Abstract:In this talk, I will explore how gravitational-wave (GW) signatures can reveal the nature of neutrino massesâ??Dirac, Majorana, or pseudo-Dirac. Within the minimal $B-L$ gauge extension of the Standard Model, I will show that Majorana neutrinos with high-scale breaking produce flat GW spectra from cosmic strings, Dirac neutrinos with low-scale breaking generate peaked spectra from first-order phase transitions, and pseudo-Dirac scenarios lead to kink-like features from domain wall annihilation. Lecturer(s): Sudip Manna From : Harish-Chandra Research Institute Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Nov 04, 2025 (1404/8/13)

	Nov 04 1404/8/13	14:00	Probing Dark Matter with Gravitational-Wave Laser Interferometers in Space Show Abstract Abstract:The discovery of gravitational waves has opened a new window for exploring the universe. This talk will discuss the use of gravitational wave observations for probing dark matter. It will focus on two types of dark matter candidates, WIMPs and ultra-light dark matter. The former can form dark matter spikes around black holes, affecting the motion of compact astrophysical objects through dynamical friction effects, thereby altering the gravitational waveforms emitted by the system, potentially observable by space-based gravitational-wave Laser Interferometers, such as LISA, Taiji and Tianqin. Ultra-light dark matter can directly interact with detectors, influencing the instruments, and can also be probed through gravitational wave experiments. Lecturer(s): Yong Tang From : University of Chinese Academy of Sciences (UCAS), Beijing, China Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Oct 28, 2025 (1404/8/6)

	Oct 28 1404/8/6	14:00	Axion Superradiance: Current Status and Future Prospects Show Abstract Abstract:Black hole superradiance is a remarkable phenomenon that allows low energy bosons, like axions, to rapidly extract the rotational energy from highly spinning black holes. In this talk, I will provide a general review how this phenomenon can lead to striking signatures, starting from the case study of non-interacting scalar fields, and then moving to the case of axions. I will highlight the immense difficulties that the community currently faces, which at the moment is impeding our ability to compute even the basic observational signatures from many of these systems, and what we need to do as a community in order overcome these challenges. I will close with a optimistic outlook at what current observations have allowed us to say, as well as what we might be able to achieve moving forward. Lecturer(s): Samuel J. Witte From : Rudolf Peierls Centre for Theoretical Physics, University of Oxford, UK Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Oct 21, 2025 (1404/7/29)

	Oct 21 1404/7/29	14:00	Multiscale Analysis of Supersymmetric Partition Functions Show Abstract Abstract:Multiscale analysis has been a cornerstone of quantum field theory (QFT) since Wilsonâ??s reformulation of the renormalization group (RG) in terms of scale separations and effective field theories. Wilsonian multiscale analysis originated in the context of perturbative QFT. While numerical RG methods have since extended its reach to non-perturbative regimes, an analytic multiscale framework beyond perturbation theory has not yet emerged. In this talk, I outline a program that develops analytic tools for multiscale analysis of QFTs in the â??cleanroomâ?� provided by supersymmetry. Supersymmetric partition functions can often be computed exactly via localization to finite-dimensional integrals, and their multiscale structure can then be probed systematically through asymptotic analysis. The hope is that by understanding this clean finite-dimensional setting, we can distill lessons and techniques that eventually carry over to the more general, infinite-dimensional path integrals of non-supersymmetric QFTs. Lecturer(s): Arash Arabi Ardehali From : Sharif University of Technology Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Oct 14, 2025 (1404/7/22)

	Oct 14 1404/7/22	14:00	Gravitational radiation reaction around a static black hole surrounded by a Dehnen-type dark matter halo Show Abstract Abstract:In this talk, I will discuss the dynamics of extreme mass ratio inspirals (EMRIs) around a Schwarzschild-like black hole embedded in a dark matter (DM) halo described by a Dehnen density profile. By analyzing the motion of a compact object in this environment, we compute the orbital period and study the evolution of key orbital parameters, such as the semi-latus rectum and eccentricity, under the influence of gravitational radiation reaction. Furthermore, we investigate the additional effects of dynamical friction and dark matter accretion on the orbital evolution. Our results show that the presence of a DM halo accelerates the decrease of both the eccentricity and semi-latus rectum compared to the vacuum case, indicating that dark matter can significantly affect the inspiral process and the resulting gravitational-wave signal. Lecturer(s): Khadije Jafarzade From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Oct 07, 2025 (1404/7/15)

	Oct 07 1404/7/15	14:00	Post-Carrollian Mechanics and Gravity Show Abstract Abstract:In this talk, we begin with a brief overview of Carrollian symmetryâ??an analogue of Galilean symmetryâ??both arising as distinct contractions of PoincarÃ© symmetry. We then introduce post-Carrollian mechanics, a framework analogous to Newtonian mechanics, featuring well-defined notions of energy, momentum, an energy-momentum relation, and a Carrollian version of Newtonâ??s second law of motion. We further present the post-Carroll-SchrÃ¶dinger equation, a quantum analogue adapted to this regime. Finally, we discuss the post-Carrollian gravitational field, which emerges as radially outwardâ??a striking departure from the inward-directed nature of Newtonian gravity. Lecturer(s): Mojtaba Najafizadeh From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Sep 30, 2025 (1404/7/8)

	Sep 30 1404/7/8	14:00	String Sandwiches & Worldsheet Quantum Equivalence Principle Show Abstract Abstract:Worldsheet theory of strings is a generic Weyl-invariant 2d gravity and is customarily quantized by requiring vanishing ofVirasoro constraints on physical string states up to spurious states. This customary choice obscures WQEP, Equivalence Principle at the Quantized Worldsheet theory level. We discuss that QWEP for closed strings can be made explicit by requiring Sandwich VirasoroConstraints (SVC), requiring vanishing of Virasoro constraints sandwiched between any two physical states. We show solutions to SVC come in four classes which are specified with whether they keep or break worldsheet parity P and/or time reversal T. The class which makes P and T manifest is associated with the usual Minkoswki worldsheet observer discussed in the string theory textbooks. The three other classes constitute Hilbert spaces of generic non-inertial worldsheet observers in which P or T or both are not broken. We apply our formulation to an accelerated worldsheet with horizons, initiating the worldsheet formulation of a thermal string theory and strings probing horizon of black holes. Lecturer(s): Mohammad Mehdi Sheikh-Jabbari From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Sep 23, 2025 (1404/7/1)

	Sep 23 1404/7/1	14:00	Constraining axial non-standard neutrino interactions with MINOS and MINOS+ Show Abstract Abstract:The increasingly precise neutrino experiments raise the hope for searching for new physics through studying the impact of Neutral Current (NC) Non-Standard Interactions (NSI) of neutrinos with matter fields. Neutrino oscillation experiments along with the Elastic Coherent Î½ Nucleus Scattering (CENS) experiments already set strong bounds on all the flavor elements of the â??vectorâ?� NC NSI. However, â??axialâ?� NC NSI can hide from these experiments. In our recent study, https://arxiv.org/abs/2509.02711, we show that the neutral current data of the MINOS and MINOS+ experiments can provide information on the axial neutral current non-standard interactions of neutrinos with the $u$ and $d$ quarks; {\it i.e.,} on $\epsilon_{\alpha \beta}^{Aq}$. We derive bounds on the $ee$, $e\tau$ and $\tau \tau$ components of these couplings and show that the MINOS(+) bounds on $\epsilon^{Aq}_{e\tau}$ and $\epsilon^{Aq}_{\tau\tau}$ are currently the world leading ones. The bound on the isospin singlet case, $\epsilon^{Au}_{\tau\tau}=\epsilon^{Ad}_{\tau\tau}$ is of particular interest because while this isospin singlet NSI is theoretically motivated, it was practically unconstrained before these results. Lecturer(s): Saeed Abbaslu From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Sep 16, 2025 (1404/6/25)

	Sep 16 1404/6/25	14:00	Women in science Show Abstract Abstract:In the first part of the talk we shall very briefly discuss the pivotal role that four female astronomer, Henrietta Swan Leavitt, Vera Rubin, Jocelyn Bell Burnell, Andrea Ghez have played in advancement of astrophysics and cosmology. This year our emphasis will be on the great contribution of Leavitt to science so we shall briefly discuss Cepheids. In the second half of the talk, we shall emphasize on the role that â??identity as a female active physicistâ?� can play to combat challenges in life, especially in these turbulant times. Lecturer(s): Yasaman Farzan From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Aug 19, 2025 (1404/5/28)

	Aug 19 1404/5/28	14:00	Exploring the Nucleon Structure Using Higher Twist Effects in Polarized Parton Distributions Show Abstract Abstract:Parton Distribution Functions (PDFs) are key to understanding the momentum and spin distributions of fundamental particles inside the nucleon, and their precise determination is crucial for rigorous tests of the Standard Model and for predicting outcomes in high-energy collider experiments. In this study, we employ Gegenbauer polynomialsâ??a set of orthogonal polynomials with strong convergence properties and superior ability to model the detailed shape of distributionsâ??to parameterize the polarized parton distribution functions (PPDFs). These polynomials are defined by two key parameters, and by fitting experimental data, unknown parameters are extracted that provide deeper insights into the protonâ??s structure. By analyzing comprehensive datasets, especially the final JLAB CLAS/EG1b data for proton and deuteron, the essential role of higher twist effects in accurately determining the PPDFs is demonstrated. The polarized structure functions of the proton, neutron, and deuteron are studied at NLO accuracy, both with and without considering higher twist effects. Additionally, the polarized Bjorken sum rule and proton helicity sum rule are examined to validate the fitting results. The findings show strong agreement with existing data and various parameterization models, indicating that this approach effectively decodes the complex structure of the nucleon and opens new horizons in understanding the behavior of fundamental particles at high energies. Lecturer(s): Hamed Abdolmaleki From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
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