4,128 research outputs found
Power spectra from an inflaton coupled to the Gauss-Bonnet term
We consider power-law inflation with a Gauss-Bonnet correction inspired by
string theory. We analyze the stability of cosmological perturbations and
obtain the allowed parameter space. We find that for GB-dominated inflation
ultra-violet instabilities of either scalar or tensor perturbations show up on
small scales. The Gauss-Bonnet correction with a positive (or negative)
coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio
in the potential-dominated case. We place tight constraints on the model
parameters by making use of the WMAP 5-year data.Comment: 5 pages, 4 figures, RevTeX, references added, published versio
On the thermalization of a Luttinger liquid after a sequence of sudden interaction quenches
We present a comprehensive analysis of the relaxation dynamics of a Luttinger
liquid subject to a sequence of sudden interaction quenches. We express the
critical exponent governing the decay of the steady-state propagator as
an explicit functional of the switching protocol. At long distances
depends only on the initial state while at short distances it is also history
dependent. Continuous protocols of arbitrary complexity can be realized with
infinitely long sequences. For quenches of finite duration we prove that there
exist no protocol to bring the initial non-interacting system in the ground
state of the Luttinger liquid. Nevertheless memory effects are washed out at
short-distances. The adiabatic theorem is then investigated with
ramp-switchings of increasing duration, and several analytic results for both
the propagator and the excitation energy are derived.Comment: 7 pages, 4 figure
d-wave Holographic Superconductor Vortex Lattice and Non-Abelian Holographic Superconductor Droplet
A d-wave holographic superconductor is studied under a constant magnetic
field by perturbation method, we obtain both droplet and triangular vortex
lattice solution. The results are the same as the s-wave holographic
superconductor. The non-Abelian holographic superconductor with -wave
background is also studied under magnetic field, unlike the d-wave and s-wave
models, we find that the non-Abelian model has only droplet solution.Comment: Version2, 12 pages,2 figures. Accepted by PR
Polarized Deep Inelastic Scattering Off the "Neutron" From Gauge/String Duality
We investigate deep inelastic scattering off the polarized "neutron" using
gauge/string duality. The "neutron" corresponds to a supergravity mode of the
neutral dilatino. Through introducing the Pauli interaction term into the
action in space, we calculate the polarized deep inelastic
structure functions of the "neutron" in supergravity approximation at large t'
Hooft coupling and finite with . In
comparison with the charged dilatino "proton," which has been obtained in the
previous work by Gao and Xiao, we find the structure functions of the "neutron"
are power suppressed at the same order as the ones of the "proton." Especially,
we find the Burkhardt-Cottingham-like sum rule, which is satisfied in the work
by Gao and Xiao, is broken due to the Pauli interaction term. We also
illustrate how such a Pauli interaction term can arise naturally from higher
dimensional fermion-graviton coupling through the usual Kaluza-Klein reduction.Comment: 21pages,5figures, published versio
Supercurrent in p-wave Holographic Superconductor
The p-wave and -wave holographic superconductors with fixed DC
supercurrent are studied by introducing a non-vanishing vector potential. We
find that close to the critical temperature of zero current, the
numerical results of both the p wave model and the model are the same as
those of Ginzburg-Landau (G-L) theory, for example, the critical current and the phase transition in the presence of a DC current is
a first order transition. Besides the similar results between both models, the
superconductor shows isotropic behavior for the supercurrent, while the
p-wave superconductor shows anisotropic behavior for the supercurrent.Comment: Version 4. 18 pages, 9figures. New results of the anisotropic
behavior for the supercurrent in p-wave model added. Accepted by PR
Entanglement conditions for multi-mode states
We provide a class of inequalities for detecting entanglements in multi-mode
systems. Necessary conditions for fully separable, bi-separable and sufficient
conditions for fully entangled states are explicitly presented.Comment: 12 page
Relativistic description of J/\psi dissociation in hot matter
The mass spectra and binding radii of heavy quark bound states are studied on
the basis of the reduced Bethe-Salpeter equation. The critical values of
screening masses for and bound states at a finite
temperature are obtained and compared with the previous results given by
non-relativistic models.Comment: 13 latex pages, 2 figure
Amplitude dynamics of charge density wave in LaTe: theoretical description of pump-probe experiments
We formulate a dynamical model to describe a photo-induced charge density
wave (CDW) quench transition and apply it to recent multi-probe experiments on
LaTe [A. Zong et al., Nat. Phys. 15, 27 (2019)]. Our approach relies on
coupled time-dependent Ginzburg-Landau equations tracking two order parameters
that represent the modulations of the electronic density and the ionic
positions. We aim at describing the amplitude of the order parameters under the
assumption that they are homogeneous in space. This description is supplemented
by a three-temperature model, which treats separately the electronic
temperature, temperature of the lattice phonons with stronger couplings to the
electronic subsystem, and temperature of all other phonons. The broad scope of
available data for LaTe and similar materials as well as the synergy
between different time-resolved spectroscopies allow us to extract model
parameters. The resulting calculations are in good agreement with ultra-fast
electron diffraction experiments, reproducing qualitative and quantitative
features of the CDW amplitude evolution during the initial few picoseconds
after photoexcitation.Comment: 21 pages, 14 figures; this version is almost identical to the
published version; comparing to the earlier arXiv submission, current version
contains a new figure (Fig.10), and a broader discussion of theoretical
results and approximation
Routes to Advanced Intermediates in the Synthesis of Tetracarbocyclic Sesquiterpenoids Daphnenoid A and Artatrovirenols A and B
A short route from dihydrocarvone is described, which led to the tetracarbocyclic core common to artatrovirenol A and B and daphnenoid A. A variant of this route afforded guaia-4,6-dien-3-one (from Enterospermum madagascarensis) and its epimer. From 2-(2-oxoethyl)furan, a 15-step sequence then delivered the complete carbon skeleton and all functionality necessary for daphnenoid A. Key steps in the route include diastereoselective intramolecular oxidopyrylium cycloaddition, oxa-bridge cleavage under “push–pull” conditions, and intramolecular Diels–Alder cycloaddition
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