36,996 research outputs found
Towards a holographic quark-hadron continuity
We study dense nuclear and quark matter within a single microscopic approach,
namely the holographic Sakai-Sugimoto model. Nuclear matter is described via
instantons in the bulk, and we show that instanton interactions are crucial for
a continuous connection of chirally broken and chirally symmetric phases. The
continuous path from nuclear to quark matter includes metastable and unstable
stationary points of the potential, while the actual chiral phase transition
remains of first order, as in earlier approximations. We show that the model
parameters can be chosen to reproduce low-density properties of nuclear matter
and observe a non-monotonic behavior of the speed of sound as a function of the
baryon chemical potential, as suggested by constraints from QCD and
astrophysics.Comment: 28+19 pages, 5 figures; v2: clarifications and references added,
version to appear in JHE
General relations for quantum gases in two and three dimensions. Two-component fermions
We derive exact relations for spin-1/2 fermions with zero-range or
short-range interactions, in continuous space or on a lattice, in or in
, in any external potential. Some of them generalize known relations
between energy, momentum distribution , pair distribution function
, derivative of the energy with respect to the scattering length
. Expressions are found for the second order derivative of the energy with
respect to (or to in ). Also, it is found that the leading
energy corrections due to a finite interaction range, are proportional to the
effective range in (and to in ) with exprimable
model-independent coefficients, that give access to the subleading short
distance behavior of and to the subleading tail of .
This applies to lattice models for some magic dispersion relations, an example
of which is given. Corrections to exactly solvable two-body and three-body
problems are obtained. For the trapped unitary gas, the variation of the
finite- and finite energy corrections within each energy
ladder is obtained; it gives the frequency shift and the collapse time of the
breathing mode. For the bulk unitary gas, we compare to fixed-node Monte Carlo
data, and we estimate the experimental uncertainty on the Bertsch parameter due
to a finite .Comment: Augmented version: with respect to published version, subsection V.K
added (minorization of the contact by the order parameter). arXiv admin note:
text overlap with arXiv:1001.077
Nonlinear theory of solitary waves associated with longitudinal particle motion in lattices - Application to longitudinal grain oscillations in a dust crystal
The nonlinear aspects of longitudinal motion of interacting point masses in a
lattice are revisited, with emphasis on the paradigm of charged dust grains in
a dusty plasma (DP) crystal. Different types of localized excitations,
predicted by nonlinear wave theories, are reviewed and conditions for their
occurrence (and characteristics) in DP crystals are discussed. Making use of a
general formulation, allowing for an arbitrary (e.g. the Debye electrostatic or
else) analytic potential form and arbitrarily long site-to-site range
of interactions, it is shown that dust-crystals support nonlinear kink-shaped
localized excitations propagating at velocities above the characteristic DP
lattice sound speed . Both compressive and rarefactive kink-type
excitations are predicted, depending on the physical parameter values, which
represent pulse- (shock-)like coherent structures for the dust grain relative
displacement. Furthermore, the existence of breather-type localized
oscillations, envelope-modulated wavepackets and shocks is established. The
relation to previous results on atomic chains as well as to experimental
results on strongly-coupled dust layers in gas discharge plasmas is discussed.Comment: 21 pages, 12 figures, to appear in Eur. Phys. J.
A pilot study comparing the metabolic profiles of elite-level athletes from different sporting disciplines
Background: The outstanding performance of an elite athlete might be associated with changes in their blood metabolic profile. The aims of this study were to compare the blood metabolic profiles between moderate- and high-power and endurance elite athletes and to identify the potential metabolic pathways underlying these differences. Methods: Metabolic profiling of serum samples from 191 elite athletes from different sports disciplines (121 high- and 70 moderate-endurance athletes, including 44 high- and 144 moderate-power athletes), who participated in national or international sports events and tested negative for doping abuse at anti-doping laboratories, was performed using non-targeted metabolomics-based mass spectroscopy combined with ultrahigh-performance liquid chromatography. Multivariate analysis was conducted using orthogonal partial least squares discriminant analysis. Differences in metabolic levels between high- and moderate-power and endurance sports were assessed by univariate linear models. Results: Out of 743 analyzed metabolites, gamma-glutamyl amino acids were significantly reduced in both high-power and high-endurance athletes compared to moderate counterparts, indicating active glutathione cycle. High-endurance athletes exhibited significant increases in the levels of several sex hormone steroids involved in testosterone and progesterone synthesis, but decreases in diacylglycerols and ecosanoids. High-power athletes had increased levels of phospholipids and xanthine metabolites compared to moderate-power counterparts. Conclusions: This pilot data provides evidence that high-power and high-endurance athletes exhibit a distinct metabolic profile that reflects steroid biosynthesis, fatty acid metabolism, oxidative stress, and energy-related metabolites. Replication studies are warranted to confirm differences in the metabolic profiles associated with athletesâ elite performance in independent data sets, aiming ultimately for deeper understanding of the underlying biochemical processes that could be utilized as biomarkers with potential therapeutic implications
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