18,858 research outputs found
Entangled spin clusters: some special features
In this paper, we study three specific aspects of entanglement in small spin
clusters. We first study the effect of inhomogeneous exchange coupling strength
on the entanglement properties of the S=1/2 antiferromagnetic linear chain
tetramer compound NaCuAsO_{4}. The entanglement gap temperature, T_{E}, is
found to have a non-monotonic dependence on the value of , the exchange
coupling inhomogeneity parameter. We next determine the variation of T_{E} as a
function of S for a spin dimer, a trimer and a tetrahedron. The temperature
T_{E} is found to increase as a function of S, but the scaled entanglement gap
temperature t_{E} goes to zero as S becomes large. Lastly, we study a spin-1
dimer compound to illustrate the quantum complementarity relation. We show that
in the experimentally realizable parameter region, magnetization and
entanglement plateaus appear simultaneously at low temperatures as a function
of the magnetic field. Also, the sharp increase in one quantity as a function
of the magnetic field is accompanied by a sharp decrease in the other so that
the quantum complementarity relation is not violated.Comment: 17 pages, 6 figures. Accepted in Phys. Rev.
A k-essence Model Of Inflation, Dark Matter and Dark Energy
We investigate the possibility for \textit{k}-essence dynamics to reproduce
the primary features of inflation in the early universe, generate dark matter
subsequently, and finally account for the presently observed acceleration. We
first show that for a purely kinetic \textit{k}-essence model the late time
energy density of the universe when expressed simply as a sum of a cosmological
constant and a dark matter term leads to a static universe. We then study
another \textit{k}-essence model in which the Lagrangian contains a potential
for the scalar field as well as a non-canonical kinetic term. We show that such
a model generates the basic features of inflation in the early universe, and
also gives rise to dark matter and dark energy at appropriate subsequent
stages. Observational constraints on the parameters of this model are obtained.Comment: 8 pages, Latex, minor changes to match with published versio
Assessing non-linear models for galaxy clustering III: Theoretical accuracy for Stage IV surveys
We provide in depth MCMC comparisons of two different models for the halo
redshift space power spectrum, namely a variant of the commonly applied
Taruya-Nishimichi-Saito (TNS) model and an effective field theory of large
scale structure (EFTofLSS) inspired model. Using many simulation realisations
and Stage IV survey-like specifications for the covariance matrix, we check
each model's range of validity by testing for bias in the recovery of the
fiducial growth rate of structure formation. The robustness of the determined
range of validity is then tested by performing additional MCMC analyses using
higher order multipoles, a larger survey volume and a more highly biased tracer
catalogue. We find that under all tests, the TNS model's range of validity
remains robust and is found to be much higher than previous estimates. The
EFTofLSS model fails to capture the spectra for highly biased tracers as well
as becoming biased at higher wavenumbers when considering a very large survey
volume. Further, we find that the marginalised constraints on for all
analyses are stronger when using the TNS model.Comment: 25 pages, 19 figures. Accepted version for publication in JCA
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