Seminars



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Wed May 25, 2022 (1401/3/4)

       

May 25
1401/3/4

18:00
 

How living matter self-organizes while breaking action-reaction symmetry

Abstract:There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized active soft matter that is away from equilibrium ``just the right way. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. In particular, I will discuss the general class of chemical activity both as the source of non-equilibrium drive and the underlying mechanism for self-organization. Cells and microorganisms produce and consume all sorts of chemicals, from nutrients to signalling molecules. The same happens at the nanoscale inside cells themselves, where enzymes catalyze the production and consumption of the chemicals needed for life. In this colloquium, I will discuss a generic mechanism by which such chemically-active particles, be it cells or enzymes or engineered synthetic colloids, can "sense" each other and ultimately self-organize in a multitude of ways. A peculiarity of these chemical-mediated interactions is that they break action-reaction symmetry: for example, one particle may be repelled from a second particle, which is in turn attracted to the first one, so that it ends up "chasing" it. Such chasing interactions allow for the formation of large clusters of particles that "swim" autonomously. Regarding enzymes, we find that they can spontaneously aggregate into clusters with precisely the right composition, so that the product of one enzyme is passed on, without lack or excess, to the next enzyme in the metabolic cascade. Finally, I will discuss how breaking the action-reaction symmetry can allow a system described by two scalar fields to exhibit spontaneous breaking of time translation, time-reversal, space translation, and polar symmetries.
Lecturer(s): Ramin Golestanian
From : Max Planck Institute for Dynamics and Self-Organization & Oxford University
Research Group: Physics Colloquium
More Info. : Link

Wed May 25, 2022 (1401/3/4)

       

May 25
1401/3/4

11:00
 

Experimentally simulating unexplored regimes of quantum walks via patterned photonic metasurfaces

Abstract:The ability to control the couplings between either confined or propagating optical modes is the basis of photonic simulators. Reproducing temporally-long evolutions of particles across large lattices is a challenging task, as required setups are complex and lossy. We proposed a novel method to do a photonic quantum walk, even hundreds of steps, by propagating a light beam through a few birefringent optical elements. We achieved up to 320 timesteps of a one-dimensional quantum walk, far beyond state-of-the-art experiments [1]. In this talk, I will introduce an optical element which we named it g-plate. It is a patterned liquid crystal metasurface which has a lot of applications in classical and quantum optics. I will briefly explain how it is possible to measure picosecond displacement by this device [2]. I will also talk about in what way it is possible to do ultra-long timesteps quantum walk with a few g-plates.
Lecturer(s): Amin Babazadeh
From : Department of Physics, University of Naples Federico II, Naples, Italy
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

Tue May 24, 2022 (1401/3/3)

       

May 24
1401/3/3

14:00
 

The mesoscopic system as quantum control elements

Abstract:Abstract My research is focused on the theoretical study of mesoscopic systems in contact with individual qubits. Here "mesoscopic system" refers to a connected network of two-level quantum systems (e.g., spin half particles) that show collective quantum behavior. Each two-level system, if studied alone, would be a quantum bit. However, individual control and measurement of each element are not available, and the mesoscopic system can be controlled collectively and measured globally. I am particularly interested in micro-macro entangled states between mesoscopic systems and qubits and using such states as control elements to connect separated qubits. This topic lies in the intersection of three interesting, seemingly unrelated subjects: interconnecting non-interacting qubits, studying fundamental questions about quantum mechanics, and out-of-equilibrium many-body quantum dynamics. In this talk, I will present my works on these three subjects. First, I will introduce the concept of micro-macro entanglement and show how it unifies the three mentioned topics. Then, I will explain how creating a micro-macro entangled state between a mesoscopic system and a qubit can facilitate entangling separated non-interacting qubits. Next, I will discuss creating micro-macro entangled states with a mesoscopic spin system, consisting of spin half particles, using experimentally available control tools and internal coupling among the spins. After that, I will show the connection to fundamental questions about quantum mechanics, such as what causes quantum to classical transition? How to extend quantum behavior to large scales? I will end my talk with future research directions and open questions.
Lecturer(s): Maryam Sadat Mirkamali
From : University of Waterloo
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed May 18, 2022 (1401/2/28)

       

May 18
1401/2/28

14:00
 

Investigation of Hyperbolic Plasmon Polaritons in a Td-WTe2 Single Layer

Abstract:Natural hyperbolic two-dimensional systems are a fascinating class of materials that could open alternative pathways to manipulating plasmon propagation and light-matter interactions. Here, we present a comprehensive study of the optical response in Td -WTe2 by means of density-functional and many-body perturbation theories. We show how monolayer WTe2 with in-plane anisotropy sustains hyperbolic plasmon polaritons, which can be tuned via chemical doping and strain. The latter is able to extend the hyperbolic regime toward the near-infrared with low losses. Moreover, WTe2 can even be switched between elliptic and hyperbolic regimes with a moderate strain. In addition, plasmons in WTe2 are characterized by low losses owing to electron-phonon scattering, which is responsible for the temperature dependence of the plasmon line width. Interestingly, the temperature can also be utilized to tune the in-plane anisotropy of the WTe2 optical response.
Lecturer(s): Zahra Torbatian
From : School of Nano Science,, IPM
Research Group: Condensed Matter and Statistical Physics Group
More Info. : Link

Tue May 17, 2022 (1401/2/27)

       

May 17
1401/2/27

14:00
 

Emergence of non-linear electrodynamic theories from $T-T^{\bar}$-like deformations

Abstract:In this letter, I investigate the deformation of the ModMax theory, as a unique Lagrangian of non-linear electrodynamics preserving both conformal and electromagnetic-duality invariance, under $T-T^{\bar}$-like flows. I show that the deformed theory is the generalized non-linear Born-Infeld electrodynamics. Being inspired by the invariance under the flow equation for Born-Infeld theories, I propose another $T-T^{\bar}$-like operator generating the ModMax and generalized Born-Infeld non-linear electrodynamic theories from the usual Maxwell and Born-Infeld theories, respectively.
Lecturer(s): Hossein Babaei-Aghbolagh
From : University of Mohaghegh Ardabili
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue May 10, 2022 (1401/2/20)

       

May 10
1401/2/20

14:00
 

Does axion warm inflation make sense as an early time cosmological model?

Abstract:In this talk, I will review the attempts that have been done to develop the idea of warm axion inflation. An important question to consider is the thermalization procedure. I will demonstrate that particle production during inflation produces a thermal plasma that contributes to inflaton evolution. The tensor power spectrum of this model can be modified to give a unique picture of warm axion inflation.
Lecturer(s): Vahid Kamali
From : Bu-Ali Sina University
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue May 10, 2022 (1401/2/20)

       

May 10
1401/2/20

14:00
 

Does axion warm inflation make sense as an early time cosmological model?

Abstract:In this talk, I will review the attempts that have been done to develop the idea of warm axion inflation. An important question to consider is the thermalization procedure. I will demonstrate that particle production during inflation produces a thermal plasma that contributes to inflaton evolution. The tensor power spectrum of this model can be modified to give a unique picture of warm axion inflation.
Lecturer(s): Vahid Kamali
From : Bu-Ali Sina University
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Wed Apr 27, 2022 (1401/2/7)

       

Apr 27
1401/2/7

14:00
 

Electron transport and interface effects in NbS2//WSe2 lateral and vertical heterostructures

Abstract:Research on two-dimensional (2D) materials has drawn enormous attention since the pioneering studies of the novel properties of graphene. Among 2D materials, the interest in the transition metal dichalcogenide (TMD2) family has grown exponentially because of their outstanding electronic and optical properties. In this talk, we investigate transport in NbS2//WSe2 lateral heterostructure (LH) and vertical heterostructure (VH). Based on DFT simulations using Quantum Espresso suite of codes and an electrostatic potential analysis, we unveil electron transmission through the scattering region and study the effects of the electronic structure of each TMD2 and their interfaces on the electron transmission. Both LH and VH have nonzero transmission below the Fermi energy, while the LH has the higher transmission. For VH, we obtain the double peak transmission and bigger interval due to having a different electronic structure. The double peak in VH transmission will be further explained in terms of a simplified but accurate model.
Lecturer(s): Zahra Golsanamlou
From : CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa, Italy
Research Group: Condensed Matter and Statistical Physics Group
More Info. : link

Tue Apr 26, 2022 (1401/2/6)

       

Apr 26
1401/2/6

12:27
 

Non-Gaussianity and Secondary Gravitational Waves from Primordial Black Holes Production in alpha-attractor Inflation

Abstract:We study the non-Gaussianity and secondary Gravitational Waves (GWs) in the process of the Primordial Black Holes (PBHs) production from inflation. In our work, we focus on the $\alpha$-attractor inflation model in which a tiny bump in the inflaton potential enhances the amplitude of the curvature perturbations at some scales and consequently leads to the PBHs production with different mass scales. We implement the computational code BINGO which calculates the non-Gaussianity parameter in different triangle configurations. Our examination implies that in this model, the non-Gaussianity gets amplified significantly in the equilateral shape around the scales in which the power spectrum of the scalar perturbations peaks. The imprints of these non-Gaussianities can be probed in the scales corresponding to the BBN and $\mu$-distortion events, or in smaller scales, and detection of such signatures in the future observations may confirm the idea of our model for the generation of PBHs or rule it out. Moreover, we investigate the secondary GWs in this framework and show that in our model, the peak of the present fractional energy density as $\Omega_{GW0} \sim 10^{-8}$ at different frequencies which depends on the model parameters. These results lie well within the sensitivity region of some GWs detectors at some frequencies, and therefore the observational compatibility of our model can be appraised by the forthcoming data from these detectors. We further provide some estimations for the tilts of the included GWs spectrum in the different intervals of frequency, and demonstrate that the spectrum obeys the power-law relation $\Omega_{GW0}\sim f^{n}$ in those frequency bands.
Lecturer(s): Kazem Rezazadeh
From : IPM, School of Physics
Research Group: HEPCO Group Weekly Seminar
More Info. : link

Tue Apr 19, 2022 (1401/1/30)

       

Apr 19
1401/1/30

14:00
 

Challenges of The Which-Way Description in the Causal Approach of Quantum Theory

Abstract:One of the alternative approaches in quantum theory is the causal approach and a deterministic view of the evolution of quantum systems. Although this approach solves many of the major problems of this theory, including the measurement problem and the classical limit, there is still debate in the scientific community about the veracity of the description that this approach provides for the evolution of particles. In the last few decades, several thought experiments have been proposed to clarify this issue, and due to the development of quantum facilities in the last decade, good experiments have been performed that show these paths are real. In this presentation, we discuss this approach and the challenges it faces.
Lecturer(s): Ali Ayatollah Rafsanjani
From : Sharif University
Research Group: HEPCO Group Weekly Seminar
More Info. : link

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