SCHOOL OF PHYSICS :: Seminars

Seminars

Title:
Research Group:
From:	To:

Tue Mar 11, 2025 (1403/12/21)

	Mar 11 1403/12/21	14:00	A proposal for a Covariant Arrow of Time Show Abstract Abstract:While fundamental formulations of physics, such as Newtonian mechanics, General Relativity (GR), and Quantum Mechanics, are time-symmetric, the universe around us is clearly not. The quest for an arrow of time has been a longstanding issue. In this talk, I propose a â??generally covariant arrow of timeâ?� based on quantum (semiclassical) considerations in GR. Lecturer(s): Shahin Sheikh Jabbari From : School of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Room C, Floor 2, Farmanieh Building, No. 70, Lavasani St. Link
Tue Feb 25, 2025 (1403/12/7)

	Feb 25 1403/12/7	14:00	Gravitational Stress Tensor and Current at Null Infinity in Three Dimensions Show Abstract Abstract:We develop the framework that reveals the intrinsic conserved stress tensor and current associated with the null infinity of a three-dimensional (3d) asymptotically flat spacetime. These are, respectively, canonical conjugates of degenerate metric and Ehresmann connection of the boundary Carrollian geometry. Their conservation reproduces the Bondi-mass and angular momentum conservation equations if the asymptotic boundary is endowed with a torsional affine connection that we specify. Our analysis and results shed further light on the 3d flat holography; the stress tensor and current give rise to an asymptotically flat fluid/gravity correspondence. The requirement of a well-defined 3d action principle yields Schwarzian action at null infinity governing the dynamics induced by reparametrizations over the celestial circle, in accord with the codimension $2$ holography of 3d flat spacetimes. Lecturer(s): Hamed Adami From : Fudan University & Shanghai institute for mathematics and interdisciplinary sciences Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Feb 18, 2025 (1403/11/30)

	Feb 18 1403/11/30	14:00	Search for CP-violation as a guiding star towards new physics Show Abstract Abstract:Within the relativistic field theory, CPT is proved to be conserved. However, CP can be broken. The violation of CP can induce electric dipole moment for elementary fermions. Indeed, CP is broken in the Standard Model (SM) of particles. However, the predicted value of the electron electric dipole moment within the SM is too small to be resolvable by present and upcoming experiments. In this talk after a short review of the phenomenological impact of CV-violation, I will discuss our project on the CP-violation carried out in collaboration with late Prof. Demir. Lecturer(s): Yasaman Farzan From : School Of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Feb 11, 2025 (1403/11/23)

	Feb 11 1403/11/23	14:00	What is the origin of cosmological neutrino mass bounds? Background versus perturbations Show Abstract Abstract:The cosmological upper bound on the total neutrino mass is the dominant limit on this fundamental parameter. Recent observations have strongly tightened it, approaching the lower limit set by oscillation data. Understanding its physical origin, robustness, and model-independence becomes pressing. In this seminar I will introduce a novel framework to explicitly separate for the first time the two distinct cosmological neutrino-mass effects. On the one hand, the impact on background evolution, related to the energy in neutrino masses; on the other hand, the "kinematic" impact on perturbations, related to neutrino free-streaming. I will didactically explain how these effects separately modify CMB anisotropies, by introducing two effective masses enclosing background and perturbations effects. I will explain the results of analyzing CMB data in this framework, which show that the neutrino-mass bound is mostly a background measurement, i.e., how the neutrino energy density evolves with time. The results also quantify the difficulty of measuring the neutrino "kinematical" mass, whose bound is relaxed by 3 orders of magnitude. Lecturer(s): Toni Bertolez Martinez From : ICCUB Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Feb 04, 2025 (1403/11/16)

	Feb 04 1403/11/16	14:00	Three unique analyses for three new neutrino detectors Show Abstract Abstract:Next-generation neutrino experiments, such as JUNO, Hyper-K, and DUNE, offer new, unique probes into neutrino and beyond the standard model physics. In this talk, I will discuss how each detector's target material (or size) will lead to distinct signatures and how they could be used in new physics and precision studies. For JUNO, we will utilize low-energy neutrino signals in Carbon to discover the atmospheric tau-neutrino flux. For DUNE, nuclear transitions in Argon allow for new and exciting measurements of solar neutrinos Ã la SNO. Finally, for Hyper-K, its size, and sensitivity to low-energy neutrinos will allow it to measure neutrinos coming from dark matter annihilating within Jupiter's core, reaching sensitivities similar to current direct detection experiments. Lecturer(s): Stephan Meighen-Berger From : University of Melbourne Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Jan 21, 2025 (1403/11/2)

	Jan 21 1403/11/2	14:13	Dark Acoustic Oscillation Faces the Cosmological Tension Show Abstract Abstract:With the growing precision of cosmological measurements, tensions in the determination of cosmological parameters have arisen that might be the first manifestations of physics going beyond Lambda CDM. We propose a new class of interacting dark sector models, which lead to qualitatively distinct cosmological behavior, dark acoustic oscillation, which can potentially simultaneously address the two most important tensions in cosmological data, the H0 and S8 tensions. The main ingredients in this class of models are self-interacting dark radiation and its dark acoustic oscillation induced by strong interactions with a fraction of dark matter. I will also present the latest results from applying this model across various combinations of cosmological data, illustrating the improvement it provides over Lambda CDM. Lecturer(s): Taewook Youn From : Cornell University, Korea Institute for Advanced Study Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Dec 31, 2024 (1403/10/11)

	Dec 31 1403/10/11	14:00	Looping story in early universe cosmology Show Abstract Abstract:We will review the ongoing debates on loop corrections in the multi-phase inflationary universe and their controversial results. Then, we will show that quantum effects can dramatically affect the long CMB-scale modes after regularizing and renormalizing divergences in different stages of inflationary evolution. Lecturer(s): Haidar Sheikhahmadi From : School Of Astronomy, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Dec 17, 2024 (1403/9/27)

	Dec 17 1403/9/27	14:00	Null Boundary Poisson Brackets Show Abstract Abstract:In physics, we often encounter different types of boundaries: spacelike, timelike, and null boundaries. Spacelike boundaries (e.g., constant time slices) are used for initial value problems, while timelike boundaries (e.g., constant radial surfaces) are suited for boundary value problems. Null boundaries are unique because they share characteristics of both, conceptually lying between spacelike and timelike boundaries. Examples include black hole horizons and null infinity in asymptotically flat spacetimes. In this talk, I will discuss Einstein's gravity in the presence of a generic null boundary and examine the structure of Poisson brackets defined on it. Key results include the ultralocal nature of these brackets and the Carrollian structure of the null boundary solution space. Lecturer(s): Vahid Taghiloo From : School Of Physics, IPM Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Dec 03, 2024 (1403/9/13)

	Dec 03 1403/9/13	14:00	Entanglement in Lifshitz Fermion Theories Show Abstract Abstract:I will discuss the static entanglement structure in (1+1)-dimensional free Dirac-fermion theory with Lifshitz symmetry, focusing on arbitrary integer dynamical critical exponents. My presentation will examine the behavior of various entanglement measures in both pure and mixed states. I will also highlight the distinctive properties of Dirac-Lifshitz fermions, particularly their locality, which contrasts with the non-local behavior of scalar counterparts and plays a crucial role in shaping their entanglement structure. Lecturer(s): Mohammad Javad Vasli From : University of Guilan Research Group: HEPCO Group Weekly Seminar More Info. : Link
Tue Nov 26, 2024 (1403/9/6)

	Nov 26 1403/9/6	14:00	A Quantum Description of Wave Dark Matter (Arxiv no: 2408.04696) Show Abstract Abstract:In this talk, I will outline a fundamentally quantum description of bosonic dark matter. Following a quantum optics inspired approach, I will show the density operator of dark matter, which takes a mixed Gaussian form over a coherent state basis. This formalism also allows a precise description of quantities related to dark matter coherence. I will further give a continuous description of dark matter through the wave-particle transition, where the density fluctuation in various scales evolves between the two limits, showing a unique behavior near the boundary of these descriptions. Lecturer(s): Dhong Yeon Cheong From : Yonsei University, Seoul, Republic of Korea Research Group: HEPCO Group Weekly Seminar More Info. : Link
	* Please Search (Top of the page) to see more seminars. *