Seminars



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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

Tue Jun 21, 2022 (1401/3/31)

       

Jun 21
1401/3/31

14:00
 

Probing charged lepton flavor violation with axion-like particles at a future muon collider

Abstract:In this talk, after a brief review of the origin of axion-like particles (ALPs), I will show how charged lepton-flavor-violating (LFV) decays of the tau lepton (if exist) with an ALP in the final state can be probed at a future muon collider. I will explain the search scenario, challenges and strategies for mitigating the background. Finally, we will compare the expected constraints on the LFV couplings obtained in this analysis with the present experimental constraints.
Lecturer(s): Gholamhossein Haghighat
From : IPM, School of Particles and Accelerators
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Jun 15, 2022 (1401/3/25)

       

Jun 15
1401/3/25

14:00
 

Two-component density functional theory for muonic molecules

Abstract: It is well-known experimentally that the positively charged muon and the muonium atom may bind to molecules and solids, and through muon�??s magnetic interaction with unpaired electrons, valuable information on the local environment surrounding the muon is deduced. Theoretical understanding of the structures and properties of the resulting muonic species requires accurate and efficient quantum mechanical computational methodologies. In this talk, the two-component density functional theory (TC-DFT) will be introduced as a possible candidate for the proper treatment of muonic systems. This approach is capable of treating the electrons and positive muon on an equal footing as quantum particles, which is beyond the domain of the purely electronic DFT framework. In addition, a novel electron-positive muon correlation functional will be offered for the first time, which serves as the main ingredient of the muonic TC-DFT methodology. The computational application of the developed method to a benchmark set of muonic organic molecules will also demonstrate its capability to elucidate the intricate interactions of the positive muon in complex molecular systems.
Lecturer(s): Mohammad Goli
From : IPM, School of Nano Science
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

Tue Jun 14, 2022 (1401/3/24)

       

Jun 14
1401/3/24

14:00
 

Quantum designs and Mutually Unbiased Measurements

Abstract:Two orthonormal bases of a Hilbert space are said to be mutually unbiased bases (MUB) if the transition probabilities from each state of the first basis to each state of the second basis are the same, irrespective of which pair of states is chosen. A complete set of MUBs is an example of a rich combinatorial structure known as complex projective 2-designs. Mutually unbiased measurements (MUM), on the other hand, are a generalization of the mutually unbiased bases in which the measurement operators need not to be rank-one projectors. Among the various applications of MUBs and MUMs, their ability in detecting quantum entanglement is one of the most recent and interesting ones. In this talk, I will briefly introduce designs, quantum designs, and mutually unbiased measurements and describe how they can be used to detect entanglement.
Lecturer(s): Seyed Javad Akhtarshenas
From : Ferdowsi University of Mashhad
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Jun 08, 2022 (1401/3/18)

       

Jun 08
1401/3/18

14:00
 

Magnetic blue-shift of Mott gaps enhanced by double-exchange Mechanism

Abstract:Strong correlations in Mott insulators induce a substantial charge excitation energy known as the Mott gap. In this talk, we discuss how the Mott gap is affected by long-range antiferromagnetic ordering upon reducing the temperature below the Neel temperature. Our finding is that the Mott gap is increased by the magnetic ordering: a magnetic blue-shift (MBS) occurs. We unveil the origin of the MBS of the Mott gap by analyzing the Hubbard model and the Hubbard-Kondo model and clarify the subtle differences. We show that in the Hubbard model the MBS is determined by the magnetic exchange coupling. In the Hubbard-Kondo model, an additional contribution proportional to the hopping is induced by the double-exchange mechanism. We describe the magnetic contribution to the band gap blue-shift observed in the optical conductivity of α-MnTe and pinpoint a hopping contribution of 64 % and a magnetic exchange contribution of 36 %. A MBS with the energy scale of the hopping and the exchange interaction bears the potential to enable spin-to-charge conversion on extreme time scales, highly promising for spintronic and magnonic applications.
Lecturer(s): Mohsen Hafez Torbati
From : Department of physics, Technical University of Dortmund, Germany
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

Tue Jun 07, 2022 (1401/3/17)

       

Jun 07
1401/3/17

14:00
 

Formation and Abundance of Late Forming Primordial Black Holes as Dark Matter

Abstract:The 'Dark Matter' (DM) is one of the mysterious components of our universe that accounts for almost 27% of its matter-energy content. Out of all the proposed dark matter candidates, 'WIMP' was thought to be the best-fitted one, yet its undetectability proved otherwise despite a decade of search. Recently Primordial Black Hole (PBH) has emerged as one of the most potent and well-studied candidates, even though there are theoretical and observational constraints on PBHs, keeping them from contributing to the whole DM density, except for a mass window of $10^{-16}$ - $10^{-10} M_{\odot}$. Recently a late PBH formation mechanism has been proposed between the epoch of Big Bang Nucleosynthesis (BBN) and Cosmic Microwave Background (CMB) photon decoupling. A natural late phase transition around redshift $10^6 \leq z \leq 10^8 $ in a strongly interacting fermion-scalar fluid gives rise to instability in the density perturbation resulting in the exponential growth of density perturbations in sub-Compton scales. It triggers the collapse and formation of an early dense halo that finally collapses into PBH due to cooling through scalar radiation. The talk's goal is to convince the audience that the PBHs formed in this manner indeed account for the total DM density of the universe and prove the existence of a temporary static phase of the halo due to the balance between fermi pressure and the attractive scalar during the PBH formation.
Lecturer(s): Amlan Chakraborty
From : Indian Institute of Astrophysics
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Jun 01, 2022 (1401/3/11)

       

Jun 01
1401/3/11

14:00
 

Collective cloaking of a cluster of electrostatically defined core-shell quantum dots in graphene

Abstract:We study the cloaking of a cluster of electrostatically defined core-shell quantum dots in graphene. Guided by the generalized multiparticle Mie theory, the Dirac electron scattering from a cluster of quantum dots is addressed. Indeed distant quantum dots may experience a sort of individual cloaking. But despite the multiple scattering of an incident electron from a set of adjacent quantum dots, collective cloaking may happen. Via a proper choice of the radii and bias voltages of shells, the two most important scattering coefficients and hence the scattering efficiency of the cluster dramatically decrease. Energy-selective electron cloaks are realizable. More importantly, clusters simultaneously transparent to electrons of different energies, are achievable. Being quite sensitive to applied bias voltages, clusters of core-shell quantum dots may be used to develop switches with high on-off ratios.
Lecturer(s): Mahdiyeh Sadrara
From : IPM, School of Nano Science
Research Group: Condensed Matter and Statistical Physics Group
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