系列学术报告及座谈会通知

系列学术报告及座谈会通知

 

Lecture 1:How physical theories are constructed: classical electrodynamics and general relativity
Abstract:
In this tutorial lecture I will review derivation of Classical Electrodynamics and General Relativity from the first principles as a demonstration of how physical theories are constructed based on the principle of least action and symmetries. I will also review solutions of Einstein equations for a static point mass, gravitational waves, evolution of the Universe and discuss Dark matter and Dark energy problems.
时间:12月12日(周一)下午4:00-5:30   
地点:基础学科大楼B253

 

Lecture 2:Vector theory of gravity: flat Universe without black holes and solution of dark energy problem
Abstract:
I will present an alternative theory of gravity which assumes that background geometry of the Universe is fixed four dimensional Euclidean space and gravity is a vector field A_k in this space which breaks the Euclidean symmetry. Direction of A_k gives the time coordinate, while perpendicular directions are spatial coordinates. Vector gravitational field is coupled to matter universally and minimally through equivalent metric f_ik which is a functional ofA_k. Such assumptions yield a unique theory of gravity, it is free of black holes and to the best of our knowledge passes all available tests. For cosmology Vector Gravity predicts the same evolution of the Universe as General Relativity with cosmological constant and zero spatial curvature. However, Vector Gravity provides explanation of dark energy as energy of gravitational field induced by the Universe expansion and yields, with no free parameters, the value of ΩΛ = 2/3 ≈ 0.67 which agrees with the recent Planck result ΩΛ = 0.686 ± 0.02. Such striking agreement with cosmological data indicates that gravity has a vector, rather than tensor, origin.
时间:12月13日(周二)下午4:00-5:30   
地点:基础学科大楼B253

 

Lecture 3:Composite theory of Photon and Graviton
Abstract:
In the Standard Model of particle physics photon is an elementary particle (gauge boson). However, there is a proposal that photon might not be an elementary particle but rather a particle formed of massless fermion-antifermion pairs. The idea dates back to 1932, when Louis de Broglie suggested that photon is composed of neutrino-antineutrino pairs. I will show how to construct a photon out of fermion-antifermion pairs properly based on the requirement of Lorentz invariance. The composite photon theory thus obtained yields a photon with all correct properties and is equivalent to conventional QED. Quantization of gravitational field in Vector theory of gravity is performed in a similar way. I will show that Quantum vector gravity is also equivalent to QED and, thus, it is a renormalizable theory. I will also demonstrate that gravitational wave signal recently measured by LIGO is compatible with Vector Gravity and produced by orbital inspiral of massive neutron stars rather than black holes.
时间:12月14日(周三)下午4:00-5:30   
地点:基础学科大楼B253

 


AMO/Quantum Optics Seminars(量子光学专题讨论会)
Seminar 1:
 Single-photon superradiance and radiation trapping by atomic shells
The collective nature of light emission by atomic ensembles yields fascinating effects such as superradiance and radiation trapping even at the single-photon level. Light emission is influenced by virtual transitions and the collective Lamb shift which yields peculiar features in temporal evolution of the atomic system. We study how two-dimensional atomic structures collectively emit a single photon. Namely, we consider spherical, cylindrical, and spheroidal shells with two-level atoms continuously distributed on the shell surface and find exact analytical solutions for eigenstates of such systems and their collective decay rates and frequency shifts. We identify states which undergo superradiant decay and states which are trapped and investigate how size and shape of the shell affects collective light emission. Our findings could be useful for quantum information storage and the design of optical switches.
 Light generation by medium moving through optical resonator

 

We show that steady nonuniform motion of a medium through an optical resonator can yield light amplification at the resonator frequency. High gain can be achieved if at the generated frequency the medium refractive index is close to zero or medium has very strong frequency dispersion. We also discuss an analogy between light amplification by a moving medium and generation of sound waves when gas flows along a tube with acoustically closed-open boundaries.

 

 Rabi oscillations produced by adiabatic pulse due to initial atomic coherence

 

If electromagnetic pulse is detuned from atomic transition frequency by amount Δ>1/τ, where τ is the turn on time of the pulse, then atomic population adiabatically follows the pulse intensity without causing Rabi oscillations. We show that if initially the atom has nonzero coherence then the adiabatic pulse yields Rabi oscillations of atomic population ρ_aa (t) and obtain analytical solutions for ρ_aa (t). Our findings can be useful for achieving generation of coherent light in the backward direction in the QASER scheme in which modulation of the coupling between light and atoms is produced by Rabi oscillations. Initial coherence can be created by sending a short resonant pulse into the medium followed by a long adiabatic pulse which leads to the light amplification in the backward direction.
时间:12月15日(周四)下午4:00-5:30   
地点:基础学科大楼B249

 


Seminar 2:
 QASER: From radio frequencies to optical domain

 

QASER is a device that generates high frequency coherent radiation by driving an atomic ensemble with a much smaller frequency. The amplification mechanism of the QASER is governed by the difference combination parametric resonance which occurs when the driving field frequency matches the frequency difference between two normal modes of the coupled light atom system. I will review the concept of the QASER making a connection with the combination resonance in a system of asymmetrically coupled parametric oscillators. I will demonstrate the QASER amplification mechanism at radio frequencies in coupled RLC circuits and microwave cavities. I will also discuss possible realization of the QASER at optical frequencies in gases and nonlinear media with negative refractive index or strong anomalous dispersion.

 

 Revision of the Maxwell-Bloch equations and single-photon superradiance

 

Interaction of atoms with quantum states of light is a long-standing problem that apart from fundamental physics has potential applications for optical quantum-state storage, quantum communication, and quantum information. A fully quantum mechanical treatment of this problem is usually very complicated mathematically. We show, however, that quantum mechanical evolution equations describing single-photon emission (absorption) by atomic ensembles can be written in a form equivalent to the semiclassical Maxwell-Bloch equations. This connection allows us to find exact analytical solutions of the fully quantum mechanical problem. We also found that semiclassical Maxwell-Bloch equations should be written in a form different from those commonly used. Namely, the classical limit of the quantum problem gives a propagation equation with the Laplacian operator on the right-hand side rather than with the second-order time derivative.
时间:12月16日(周五)下午4:00-5:30   
地点:基础学科大楼B249

 

报告人简介:
Anatoly A. Svidzinsky is a research associate professor in Department of Physics & Astronomy of Texas A&M University, a theoretical Physicist doing research on Quantum optics, Bose-Einsten condensation, Superconductivity, Chemical physics and Astrophysics. He received Ph.D. in Physics Degree from Moscow Institute of Physics and Technology (Russia) in 1997, and Ph.D. in Physics from Stanford University 2001. He had given talks at 90 conferences and have about 100 publications in Nature, Phys.Rev., etal. . His current citation index is about 2800 and H-index is 27.

报告&座谈会简表

报告人:Anatoly A. Svidzinsky

时间

地点

题目

12月12日4:00-5:30pm

基础学科大楼B253

Lecture 1:How physical theories are constructed: classical electrodynamics and general relativity

12月13日4:00-5:30pm

基础学科大楼B253

Lecture 2:Vector theory of gravity: flat Universe without black holes and solution of dark energy problem

12月14日4:00-5:30pm

基础学科大楼B253

Lecture 3:Composite theory of Photon and Graviton

12月15日4:00-5:30pm

基础学科大楼B249

Seminar 1:

1.Single-photon superradiance and radiation trapping by atomic shells

2.Light generation by medium moving through optical resonator

3. Rabi oscillations produced by adiabatic pulse due to initial atomic coherence

12月16日4:00-5:30pm

基础学科大楼B249

Seminar 2:

1.QASER: From radio frequencies to optical domain

2.Revision of the Maxwell-Bloch equations and single-photon superradiance