Research Group:  



Tue Dec 07, 2021 (1400/9/16)


Dec 07


Black Hole Thermodynamics: Then and Now

Abstract:I will review the subject black hole thermodynamics as it developed in the 1970's, and then explain something of the more contemporary developments that revolve around a microscopic notion of �??entropy�?�.
Lecturer(s): Edward Witten
From : Institute for Advanced Study, Princeton
Research Group: HEPCo Group Weekly Seminar
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Wed Nov 24, 2021 (1400/9/3)


Nov 24


Environmental fate of 2D materials in aquatic ecosystems: the case of graphene oxide 2D membranes

Abstract:An increasing number of 2D materials are being deployed for different applications across energy generation, conversion and storage sectors. Among these materials, however, graphene oxide and not graphite oxide, as the most technologically relevant 2D material of choice for energy-related applications, has gained a stronghold and is near the final stage of commercialization ready to enter the mass market. This calls for a thorough understanding of the behaviour of this intriguing atomically thin material and possibly other members of the mushrooming family of 2D materials in aquatic environment as their toxicity can easily pose a threat to aquatic life at global levels not seen before due to the huge surface area of 2D materials (~2000 m2/g). Although a great deal of research has been dedicated to this subject, a key misconception is the treatment of these materials as a sphere with an effective radius or that their flat surface would fold upon itself resulting in a much lower aspect ratio and consequently lower available surface area. This essentially implies a much higher critical concentration at which it is alleged that these 2D materials are toxic to the aqueous environment. Our findings presented here point out that this is not a valid assumption by showing that 2D materials in saline waters hold their flat morphology and therefore pose a greater challenge for the environment rather than their professed 3D conformed counterparts.
Lecturer(s): Seyed Hamed Aboutalebi
From : Condensed Matter National Laboratory, IPM
Research Group: Condensed Matter and Statistical Physics Group Weekly Seminar
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Tue Nov 23, 2021 (1400/9/2)


Nov 23


Unearthing String Theory In Supersymmetric Field Theories With Compact Moduli

Abstract:I will review some universal features of quantum gravity and use them to narrow the space of field theories with minimal supersymmetry in d > 6. We will see that the restrictions in 9d do not allow theories that have not been already realized in string theory. This observation demonstrates the validity of the String Lamppost Principle that all consistent theories of quantum gravity are in the String Landscape.
Lecturer(s): Alek Bedroya
From : Harvard University
Research Group: HEPCo Group Weekly Seminar
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Wed Nov 10, 2021 (1400/8/19)


Nov 10


Floquet Engineering of Topological Insulators

Abstract:Recent technological progresses in mid-infrared lasers have established a new route for engineering of the electronic band structure. Indeed, an interplay between the periodicity of lattice and time originated from the oscillating field extends the Hilbert space by inducing the so-called Floquet-Bloch states and enables one to modify the band structure (opening the gaps) and to engineer phase transitions at will by using photon-assisted processes. Fortunately, such light-induced states have been experimentally observed on the surface of irradiated topological insulators, optical lattices, graphene etc. Many striking phenomena are predicted or observed in this field: light-induced Hall conductivity, light-induced QAHI on TI�??s, etc. However, experimental challenge would be huge heating rate when the system is irradiated by the laser. In this talk, I will present a short review on the Floquet theory including on- and off- resonant regimes, the gap opening and emergence of topological phases accompanied by anomalous edge states. Then I will focus on the special case of magnetically topological insulator thin film irradiated by circularly-polarized electromagnetic field in the off-resonant regime. Fascinating feature of distinct phases emerges in the phase diagram depending on the frequency and intensity of the light as well as the system parameters and also magnetic field. We also try to go through the on-resonant regime and calculate optical conductivity of this driven system.
Lecturer(s): Hosein Cheraghchi
From : Damghan University
Research Group: Condensed Matter and Statistical Physics Group Weekly Seminar
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Tue Nov 02, 2021 (1400/8/11)


Nov 02


Holography of Information and Massive Islands

Abstract:We will review recent results that suggest that, in any standard theory of quantum gravity, information available on the bulk of a Cauchy slice must also be available near the boundary of the slice. These ideas indicate how holography should be extended to four-dimensional asymptotically flat spacetimes but they also shed light on the origins of AdS/CFT. We contrast this picture with the paradigm of islands and argue that islands are consistent only in theories of massive gravity.
Lecturer(s): Survat Raju
From : ICTS (Tata Institute of Fundamental Research)
Research Group: HEPCo Group Weekly Seminar
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Wed Oct 27, 2021 (1400/8/5)


Oct 27


An Amelioration for the Sign Problem: Adiabatic Quantum Monte Carlo

Abstract:In this talk, I will introduce the adiabatic quantum Monte Carlo (AQMC) method, where we gradually crank up the interaction strength, as an amelioration of the sign problem. It is motivated by the adiabatic theorem and will approach the true ground-state if the evolution time is long enough. I will demonstrate that the AQMC enhances the average sign exponentially such that low enough temperatures can be accessed and ground-state properties probed. It is a controlled approximation that satisfies the variational theorem and provides an upper bound for the ground-state energy. I will first benchmark the AQMC vis-à-vis the undoped Hubbard model on the square lattice which is known to be sign-problem-free within the conventional quantum Monte Carlo formalism. Next, I will test the AQMC against the density-matrix-renormalization-group approach for the doped four-leg ladder Hubbard model and demonstrate its remarkable accuracy. As a nontrivial example, I will apply our method to the Hubbard model at p=1/8 doping for a 16�?8 system and discuss its ground-state properties. I will finally utilize our method and demonstrate the emergence of U(1)2�?�SU(2)1 topological order in a strongly correlated Chern insulator.
Lecturer(s): Abolhassan Vaezi
From : Sharif University of Technology
Research Group: Condensed Matter and Statistical Physics Group Weekly Seminar
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Wed Oct 13, 2021 (1400/7/21)


Oct 13


Localization and delocalization in one-dimensional Anderson model with a general hopping matrix

Abstract:Much of our present understanding of wave-function localization in one spatial dimension is based on the original Anderson model on a one-dimensional lattice. The experimental simulation of this model using cold atoms, owing to the high degree of control over system parameters, has made possible the direct observation of localization of matter waves. In this talk, after giving an introduction to Anderson localization, I will present some new results on localization properties of this model with a general hopping matrix.
Lecturer(s): Reza Sepehrinia
From : University of Tehran
Research Group: Condensed Matter and Statistical Physics Group Weekly Seminar
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Tue Oct 12, 2021 (1400/7/20)


Oct 12



Abstract:By using complex-variable methods one can extend conventional Hermitian quantum theories into the complex domain. The result is a huge and exciting new class of non-Hermitian parity-time-symmetric (PT-symmetric) theories that still obey the fundamental laws of quantum mechanics. These new theories have remarkable physical properties, which are currently under intense study by theorists and experimentalists. Many theoretical predictions have been verified in recent beautiful laboratory experiments.
Lecturer(s): Carl M. Bender
From : Washington University in St. Louis
Research Group: HEPCo Group Weekly Seminar
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Wed Sep 29, 2021 (1400/7/7)


Sep 29


Evolutionary Dynamics on Complex Networks: A Mean Field Approach

Abstract:Mathematical models of evolution have attracted considerable attention in recent years. The main ingredients of such models are "selection", "reproduction", and "mutation". Furthermore, population structure plays an important role in evolution. "Evolutionary Graph Theory" is a powerful tool to study the interplay between population structure and evolutionary dynamics. In this talk, we try to give a brief review of this theory and then we mention to a number of recent results, among them is the effect of network topology on fixation time and fixation probability of mutants. Furthermore we propose a mean field approach to obtain the fixation time analytically for some network topologies.
Lecturer(s): Keivan Aghababaei Samani
From : Isfahan University of Technology
Research Group: Condensed Matter and Statistical Physics Group Weekly Seminar
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Tue Sep 21, 2021 (1400/6/30)


Sep 21


Geometry of Corners

Abstract:In this talk, I will first introduce the notion of corners, motivating why they are central in gauge theories. I will then discuss the geometric structure of a generic embedding of an isolated corner. This will allow us to derive the maximal embedded algebra for this corner, establishing thereof a general result, prior to a specific dynamics and gauge fixing. A family of bulk metrics adapted to the corner embedding will then be introduced, and used in Einstein gravity to derive Noether charges. The charge algebra, once the embedding map is dealt with carefully, turns out to be a centerless faithful representation of the vector fields algebra. Time permitting, I will apply our general construction to near horizon symmetries for black holes.
Lecturer(s): Luca Ciambelli
From : Physique Mathématique des Interactions Fondamentales, Université Libre de Bruxelles & International Solvay Institutes
Research Group: HEPCo Group Weekly Seminar
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