Seminars



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Tue Aug 02, 2022 (1401/5/11)

       

Aug 02
1401/5/11

14:00
 

Generalized Volume-Complexity For Two-Sided Hyperscaling Violating Black Branes

Abstract:In this talk, I will first briefly review generalized volume-complexity $\mathcal{C}_{\rm gen}$ which was recently introduced in [arXiv:2111.02429]. This quantity is an extension of volume in the Complexity=Volume (CV) proposal, by adding higher curvature corrections with a coupling constant $\lambda$ to the volume functional. Next, I will talk about the calculation of $\mathcal{C}_{\rm gen}$ for two-sided Hyperscaling Violating (HV) black branes in $d+2$ dimensions for different values of the hyperscaling violation exponent $\theta$ and dynamical exponent $z$. It is observed that $\mathcal{C}_{\rm gen}$ always grows linearly at late times provided that we choose $\lambda$ properly. Moreover, it approaches its late time value from below. I will also discuss the dependence of the growth rate of $\mathcal{C}_{\rm gen}$ on $d$, $\theta$, $z$ and $\lambda$. In the end, I will report our results for the complexity of formation obtained from volume-complexity and show that it is not UV divergent. I will also discuss its dependence on the thermal entropy and temperature of the black brane.
Lecturer(s): Farzad Omidi
From : School of Physics, IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Jul 26, 2022 (1401/5/4)

       

Jul 26
1401/5/4

14:00
 

On complex coordinate transformations

Abstract:Abstract Since the Newman-Janis paper, we know an exciting complex coordinate transformation that maps Schwarzschild solution to Kerr and Reissner�??Nordström to Kerr-Newman. A similar transformation maps the Coulomb field to a fascinating electromagnetic field dubbed "the magic field". Other complex coordinate or mixed parameter-coordinate transformations map solutions of Einstein-Maxwell theory into each other. I review some of these transformations and comment on the Newman-Janis as well as another complex transformation that preserves the Kerr-NUT set of solutions.
Lecturer(s): Sajad Aghapour
From : Max Planck Institute
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Tue Jul 19, 2022 (1401/4/28)

       

Jul 19
1401/4/28

14:00
 

Remarks on memory effect, electric-magnetic duality, and holonomy

Abstract:I will describe some aspects of the "gravitational electric-magnetic duality". Then, I will show that the generator of this symmetry appears naturally in the net rotation caused by gravitational waves on the spin of a freely falling gyroscope. Then latter, which we call the "gyroscopic memory" is in principle observable.
Lecturer(s): Ali Seraj
From : Centre for Gravitational Waves, university of bruxelles
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Jul 12, 2022 (1401/4/21)

       

Jul 12
1401/4/21

14:00
 

Accelerating black holes: Gravitational lensing and timelike geodesics

Abstract:Abstract Accelerating supermassive black holes, connected to cosmic strings, could contribute to structure formation and get captured by galaxies if their velocities are small. This would mean that the acceleration of these black holes is small too. Such a slow acceleration has no significant effect on the shadow of such supermassive black holes. We also show that, for slowly accelerating black holes, the angular position of images in the gravitational lensing effects does not change significantly. We propose a method to observe the acceleration of these black holes through gravitational lensing. The method is based on the observation that differential time delays associated with the images are substantially different with respect to the case of non-accelerating black holes. We also study the geodesics of massive particles around accelerating Schwarzschild black holes.
Lecturer(s): Mohammad Bagher Jahani Poshteh
From : School of Physics,IPM
Research Group: HEPCO Group Weekly Seminar
More Info. : Link

Tue Jul 12, 2022 (1401/4/21)

       

Jul 12
1401/4/21

12:13
 

Valorization of carbon dioxide to cyclic carbonate using silica/organosilica mesoporous materials

Abstract:In recent years, human activities, the rapid growth of industrialization, and especially the uncontrolled combustion of fossil fuels have unfortunately resulted in the increase of atmospheric concentration of carbon dioxide (CO2), as a component of greenhouses gases. The long-term effects of this trend have ensued global warming, ice melting, ocean warming, sea-level rising, and ocean acidification which are overall defined as global climate change. Consequently, the development of new carbon capture and utilization systems enabled to minimize CO2 emissions, has become the hottest topic in the scientific communities. On the other hand, CO2 is turned over in the organic chemist's mind as a resource rather than a waste product since it is an abundant, non-toxic, cheap, and renewable C1 feedstock. Therefore, the conversion of anthropogenic CO2 into high value-added chemicals, if performed in a promising sustainable approach, is receiving considerable and ever-increasing attentions. In this context, the direct coupling of CO2 with epoxides not only is significantly interested owing to the eco-friendly and more carbon-balanced approach, but also the resulting five-membered cyclic carbonates are widely used as polar aprotic solvents, electrolytes in lithium-ion batteries, and chemical intermediates in fine chemicals syntheses. However, CO2 is thermodynamically stable and the use of the catalyst for this conversion would be mandatory. Despite a variety of metal and organocatalysts have been so far reported for cyclization reaction between carbon dioxide and epoxides, the development of simple and low-cost systems which met eco-friendly, green and sustainable chemistry viewpoints, under solvent-free and mild temperature (<100 °C) and pressure (1-10 bar) have remained with many challenges. In this presentation, I am going to talk about our recent supported metal and organocatalysts on the mesoporous materials that have been described for direct CO2 valorization to cyclic carbonate.
Lecturer(s): Mojtaba Khorasani
From : Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran
Research Group: Condensed Matter and Statistical Physics Group
More Info. : Link

Wed Jul 06, 2022 (1401/4/15)

       

Jul 06
1401/4/15

14:00
 

Quasiparticle properties in doped monolayer MoS2

Abstract:One of the appealing features of MoS2 and TMDs, in general, is their external controllability of the quantum many-body properties. In particular, the environmental sensitivity of the Coulomb interaction in these materials is remarkable which has crucial consequences in the determination of the quasiparticle properties through further screening effects. In this talk, I will present a theoretical analysis in order to determine a comprehensive picture of the quasiparticle features of monolayer MoS2 and also of the extrinsic variables affecting them based on a full random-phase-approximation (RPA) self-energy calculation in the framework of Landau Fermi liquid theory. I will show how the quasi-2D character of the Coulomb interaction in this system tends to stabilize the Fermi liquid picture. Also, the important quasiparticle band-gap renormalization induced by the doped carriers in monolayer MoS2 will be discussed
Lecturer(s): Azadeh Faridi
From : School of Physics,IPM
Research Group: Condensed Matter and Statistical Physics Group
More Info. : Link

Wed Jun 29, 2022 (1401/4/8)

       

Jun 29
1401/4/8

18:00
 

Disease Ecology from Perspectives of Physics

Abstract:Here I will review my recent works [1-14] on modeling interacting contagious dynamics, for example coupled SIR or SIS dynamics, in mean field approximations and also on different random generated or empirical complex networks. I show and discuss how our recent results have been improving our understanding and prediction of epidemic dynamics and disease ecology while raising new questions and challenges in physics of critical phenomena. Also I will briefly discuss SARS-COV-2 from the perspective of disease ecology and present my recent studies on "behavioral responses to the COVID-19 spread"; which focus on the analysis and modelling of empirical data including testing strategies, air traffic, urban mobility, inequality (socio-economic classes), news spread, etc. in Iran or USA or globally.
Lecturer(s): Fakhteh Ghanbarnejad
From : Sharif University of Technology
Research Group: Physics Colloquium
More Info. : Link

Wed Jun 29, 2022 (1401/4/8)

       

Jun 29
1401/4/8

13:00
 

Fingerprinting local environments with application to machine learning interatomic potentials

Abstract:A class of supervised machine learning approaches aims at predicting a quantity from an input data vector. For example, it is common practice to recognize a person's face from the set of data points (pixels) in a digital image frame. The same techniques are effectively useful in computational condensed matter physics problems for the prediction of atomic contributions to a given physical quantity from the arrangement of the neighboring atoms of the individual atoms. Then one needs a "descriptor" that quantifies the environment of an atom such that it can be fed as input to a supervised machine learning tool. We review the basic ideas, techniques, and challenges of fingerprinting the local environment as an essential ingredient of training interatomic potentials from e.g. ab initio reference samples. We exemplify the local fingerprinting by applying it to predict the excited and ground-state energy surfaces of large atomic systems.
Lecturer(s): Ali Sadeghi
From : Physics Department, Shahid Beheshti University, Tehran, Iran
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

Tue Jun 28, 2022 (1401/4/7)

       

Jun 28
1401/4/7

14:00
 

Distorted Black Holes in Higher Dimensions

Abstract:In this talk, I will analyze the concept of a distorted black hole. As examples, I focus on the case of distorted black holes in higher dimensions and the most common generating techniques. In particular, I represent the distorted black ring solution and some of its interesting properties.
Lecturer(s): Shohreh Abdolrahimi
From : California State Polytechnic University
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Jun 22, 2022 (1401/4/1)

       

Jun 22
1401/4/1

14:00
 

Optimization by a quantum reinforcement algorithm

Abstract:Providing an optimal path to a quantum annealing algorithm is key to find good approximate solutions to computationally hard optimization problems. Reinforcement is one of the strategies that can be used to circumvent the exponentially small energy gaps of the system in the annealing process. We take a local entropy in the configuration space for the reinforcement and apply the algorithm to a number of easy and hard optimization problems.
Lecturer(s): Abolfazl Ramezanpour
From : Department of Physics, School of Sciences, Shiraz University
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

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