5,324 research outputs found
Coupled mode effects on energy transfer in weakly coupled, two-temperature plasmas
The effects of collective modes on the temperature relaxation in fully ionized, weakly coupled plasmas are investigated. A coupled mode (CM) formula for the electron-ion energy transfer is derived within the random phase approximation and it is shown how it can be evaluated using standard methods. The CM rates are considerably smaller than rates based on Fermi's golden rule for some parameters and identical for others. It is shown how the CM effects are connected to the occurrence of ion acoustic modes and when they occur. Interestingly, CM effects occur also for plasmas with very high electron temperatures; a regime, where the Landau–Spitzer approach is believed to be accurate
Slow light in moving media
We review the theory of light propagation in moving media with extremely low
group velocity. We intend to clarify the most elementary features of
monochromatic slow light in a moving medium and, whenever possible, to give an
instructive simplified picture
Simulation of Cosmic Ray neutrinos Interactions in Water
The program CORSIKA, usually used to simulate extensive cosmic ray air
showers, has been adapted to a water medium in order to study the acoustic
detection of ultra high energy neutrinos. Showers in water from incident
protons and from neutrinos have been generated and their properties are
described. The results obtained from CORSIKA are compared to those from other
available simulation programs such as Geant4.Comment: Talk presented on behalf of the ACoRNE Collaboration at the ARENA
Workshop 200
Pion and Kaon Condensation at Finite Temperature and Density
In this paper, we study O(2N)-symmetric -theory at finite temperature
and density using the 2PI-1/N expansion. As specific examples, we consider pion
condensation at finite isospin chemical potential and kaon condensation at
finite chemical potential for hyper charge and isospin charge. We calculate the
phase diagrams and the quasiparticle masses for pions and kaons in the large-N
limit. It is shown that the effective potential and the gap equation can be
renormalized by using local counterterms for the coupling constant and mass
parameter, which are independent of temperature and chemical potentials.Comment: 10 pages. 7 Figures. v2: Better plots and figs. Added significant
number of refs v3: Accepted for publication in PRD. Added a figure and
improved part on renormalization as well as presentatio
The relativistic massless harmonic oscillator
A detailed study of the relativistic classical and quantum mechanics of the
massless harmonic oscillator is presented.Comment: 15 pages, 4 figure
Temperature dependence of the spin susceptibility of a clean Fermi gas with repulsion
Spin susceptibility of a clean Fermi gas with repulsion in any dimension is
considered using a supersymmetric low energy theory of interacting spin
excitations and renormalization scheme recently proposed by Aleiner and Efetov
[cond-mat/0602309]. We generalize this method to include the coupling to the
magnetic field. As a result, we obtain for the correction to the
Pauli susceptibility a non-analytic temperature dependence of the form in dimensions where is an
effective -dependent logarithmically renormalized backscattering amplitude.
In one dimension, is proportional to , and we
reproduce a well known result obtained long ago by a direct calculation.Comment: 25 pages, 10 figure
Quantum versus classical phase-locking transition in a driven-chirped oscillator
Classical and quantum-mechanical phase locking transition in a nonlinear
oscillator driven by a chirped frequency perturbation is discussed. Different
limits are analyzed in terms of the dimensionless parameters and
( and being the driving amplitude,
the frequency chirp rate, the nonlinearity parameter and the linear frequency
of the oscillator). It is shown that for , the passage
through the linear resonance for above a threshold yields classical
autoresonance (AR) in the system, even when starting in a quantum ground state.
In contrast, for , the transition involves
quantum-mechanical energy ladder climbing (LC). The threshold for the
phase-locking transition and its width in in both AR and LC limits are
calculated. The theoretical results are tested by solving the Schrodinger
equation in the energy basis and illustrated via the Wigner function in phase
space
Three-body collisions in Boltzmann-Uehling-Uhlenbeck theory
Aiming at a microscopic description of heavy ion collisions in the beam
energy region of about 10 A GeV, we extend the Giessen
Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model by including a relativistic
mean field, in-medium baryon-baryon cross sections and three-body collisions.
The model is then compared with experimental data for central Au+Au collisions
at 2-10 A GeV and central Pb+Pb collisions at 30 and 40 A GeV on the proton
rapidity spectra, the midrapidity yields of , and
, and the transverse mass spectra of and .
The three-body collisions increase the inverse slope parameters of the hadron
-spectra to a good agreement with the data.Comment: 26 pages, 9 figures, figures added, discussion extended, results not
changed, version accepted in Phys. Rev.
Mottness: Identifying the Propagating Charge Modes in doped Mott Insulators
High-temperature superconductivity in the copper-oxide ceramics remains an
unsolved problem because we do not know what the propagating degrees of freedom
are in the normal state. As a result, we do not know what are the weakly
interacting degrees of freedom which pair up to form the superconducting
condensate. That the electrons are not the propagating degrees of freedom in
the cuprates is seen most directly from experiments that show spectral weight
redistributions over all energy scales. Of course, the actual propagating
degrees of freedom minimize such spectral rearrangements. This review focuses
on the range of epxerimental consequences such UV-IR mixings have on the normal
state of the cuprates, such as the pseudogap, mid-infrared band, temperature
dependence of the Hall number, the superfluid density, and a recent theoretical
advance which permits the identification of the weakly interacting degrees of
freedom in a doped Mott insulator. Within this theory, we show how the wide
range of phenomena which typify the normal state of the cuprates arises
including linear resistivity.Comment: To appear as a Colloquium in the April issue of Rev. Mod. Phys
Updated version contains new references and a clarification concerning Fig.
8
The J1-J2 model: First order phase transition versus deconfinement of spinons
We revisit the phase transition from the N\'eel ordered to a valence bond
solid (VBS) state in the two-dimensional antiferromagnetic Heisenberg
model. In the first part we address the question whether or not this transition
could be an example of a second order phase transition due to a deconfinement
of spinons. We give arguments based on series expansion and spin-wave theory
that this is not the case and the transition is most likely first order. The
method proposed here to detect first order phase transitions seems to be very
sensitive and might be useful in other models as well. In the second part we
analyze possible VBS patterns in the magnetically disordered phase based on
numerical data for different susceptibilities, obtained in the ordered phase,
which test the breaking of lattice symmetries. We conclude that a columnar
dimerization pattern is the most likely candidate.Comment: 7 pages, 7 figures, small changes, references adde
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