1,416 research outputs found
Hydrodynamic Modes in a Trapped Strongly Interacting Fermi Gases of Atoms
The zero-temperature properties of a dilute two-component Fermi gas in the
BCS-BEC crossover are investigated. On the basis of a generalization of the
variational Schwinger method, we construct approximate semi-analytical formulae
for collective frequencies of the radial and the axial breathing modes of the
Fermi gas under harmonic confinement in the framework of the hydrodynamic
theory. It is shown that the method gives nearly exact solutions.Comment: 11 page
Imaginary-time formulation of steady-state nonequilibrium: application to strongly correlated transport
We extend the imaginary-time formulation of the equilibrium quantum many-body
theory to steady-state nonequilibrium with an application to strongly
correlated transport. By introducing Matsubara voltage, we keep the finite
chemical potential shifts in the Fermi-Dirac function, in agreement with the
Keldysh formulation. The formulation is applied to strongly correlated
transport in the Kondo regime using the quantum Monte Carlo method.Comment: 5 pages 3 figure
A systematic study of non-ideal contacts in integer quantum Hall systems
In the present article we investigate the influence of the contact region on
the distribution of the chemical potential in integer quantum Hall samples, as
well as the longitudinal and Hall resistance as a function of the magnetic
field. First we use a standard quantum Hall sample geometry and analyse the
influence of the length of the leads where current enters/leaves the sample and
the ratio of the contact width to the width of these leads. Furthermore we
investigate potential barriers in the current injecting leads and the
measurement arms in order to simulate non-ideal contacts. Second we simulate
nonlocal quantum Hall samples with applied gating voltage at the metallic
contacts. For such samples it has been found experimentally that both the
longitudinal and Hall resistance as a function of the magnetic field can change
significantly. Using the nonequilibrium network model we are able to reproduce
most qualitative features of the experiments.Comment: 29 pages, 16 Figure
Quantum simulation of manybody effects in steady-state nonequilibrium: electron-phonon coupled quantum dots
We develop a mapping of quantum steady-state nonequilibrium to an effective
equilibrium and solve the problem using a quantum simulation technique. A
systematic implementation of the nonequilibrium boundary condition in
steady-state is made in the electronic transport on quantum dot structures.
This formulation of quantum manybody problem in nonequilibrium enables the use
of existing numerical quantum manybody techniques. The algorithm coherently
demonstrates various transport behaviors from phonon-dephasing to I-V staircase
and phonon-assisted tunneling.Comment: 5 pages, 4 figure
Microscopic Theory for the Markovian Decay of Magnetization Fluctuations in Nanomagnets
We present a microscopic theory for the phonon-driven decay of the
magnetization fluctuations in a wide class of nanomagnets where the dominant
energy is set by isotropic exchange and/or uniaxial anisotropy. Based on the
Zwanzig-Mori projection formalism, the theory reveals that the magnetization
fluctuations are governed by a single decay rate , which we further
identify with the zero-frequency portion of the associated self-energy. This
dynamical decoupling from the remaining slow degrees of freedom is attributed
to a conservation law and the discreteness of the energy spectrum, and explains
the omnipresent mono-exponential decay of the magnetization over several
decades in time, as observed experimentally. A physically transparent
analytical expression for is derived which highlights the three
specific mechanisms of the slowing down effect which are known so far in
nanomagnets.Comment: 7 page
Flow structure beneath periodic waves with constant vorticity under strong horizontal electric Fields
While several articles have been written on Electrohydrodynamics (EHD) flows
or flows with constant vorticity separately, little is known about the extent
to which the combined effects of EHD and constant vorticity affect the flow.
This study aims to fill this gap by investigating how a horizontal electric
field and constant vorticity jointly influence the free surface and the
emergence of stagnation points. Using the Euler equations framework, we employ
conformal mapping and pseudo-spectral numerical methods. Our findings reveal
that increasing the electric field intensity eliminates stagnation points and
smoothen the wave profile. This implies that a horizontal electric field acts
as a mechanism for the elimination of stagnation points within the fluid body
Self-consistent theory of turbulence
A new approach to the stochastic theory of turbulence is suggested. The
coloured noise that is present in the stochastic Navier-Stokes equation is
generated from the delta-correlated noise allowing us to avoid the nonlocal
field theory as it is the case in the conventional theory. A feed-back
mechanism is introduced in order to control the noise intensity.Comment: submitted to J.Tech. Phys.Letters (St. Petersburg
Collective Excitations of Strongly Interacting Fermi Gases of Atoms in a Harmonic Trap
The zero-temperature properties of a dilute two-component Fermi gas in the
BCS-BEC crossover are investigated. On the basis of a generalization of the
Hylleraas-Undheim method, we construct rigorous upper bounds to the collective
frequencies for the radial and the axial breathing mode of the Fermi gas under
harmonic confinement in the framework of the hydrodynamic theory. The bounds
are compared to experimental data for trapped vapors of Li6 atoms.Comment: 11 pages, 2 figure
Activated Ion Electron Capture Dissociation (AI ECD) of proteins: synchronization of infrared and electron irradiation with ion magnetron motion.
Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a CO(2) laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion. This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides (tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and measured on the time scale longer than the period of ion magnetron motion
Information theory in the study of anisotropic radiation
Information theory is used to perform a thermodynamic study of non
equilibrium anisotropic radiation. We limit our analysis to a second-order
truncation of the moments, obtaining a distribution function which leads to a
natural closure of the hierarchy of radiative transfer equations in the
so-called variable Eddington factor scheme. Some Eddington factors appearing in
the literature can be recovered as particular cases of our two-parameter
Eddington factor. We focus our attention in the study of the thermodynamic
properties of such systems and relate it to recent nonequilibrium thermodynamic
theories. Finally we comment the possibility of introducing a nonequilibrium
chemical potential for photons.Comment: 1 eps figure upon request by e-mail, to appear in Journal of Physics
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