57,158 research outputs found
Unconventional critical activated scaling of two-dimensional quantum spin-glasses
We study the critical behavior of two-dimensional short-range quantum spin
glasses by numerical simulations. Using a parallel tempering algorithm, we
calculate the Binder cumulant for the Ising spin glass in a transverse magnetic
field with two different short-range bond distributions, the bimodal and the
Gaussian ones. Through an exhaustive finite-size scaling analysis, we show that
the universality class does not depend on the exact form of the bond
distribution but, most important, that the quantum critical behavior is
governed by an infinite randomness fixed point.Comment: 6 pages, 6 figure
Electromagnetic fields and transport coefficients in a hot pion gas
We present recent results on finite temperature electromagnetic form factors
and the electrical conductivity in a pion gas. The standard Chiral Perturbation
Theory power counting needs to be modified for transport coefficients. We pay
special attention to unitarity and to possible applications for dilepton and
photon production.Comment: 4pp, 2 figures, talk given at "Strong and Electroweak Matter 2006",
BNL, May 200
On the kinematic evolution of young local associations and the Sco-Cen complex
Context: Over the last decade, several groups of young (mainly low-mass)
stars have been discovered in the solar neighbourhood (closer than ~100 pc),
thanks to cross-correlation between X-ray, optical spectroscopy and kinematic
data. These young local associations -- including an important fraction whose
members are Hipparcos stars -- offer insights into the star formation process
in low-density environments, shed light on the substellar domain, and could
have played an important role in the recent history of the local interstellar
medium. Aims: To study the kinematic evolution of young local associations and
their relation to other young stellar groups and structures in the local
interstellar medium, thus casting new light on recent star formation processes
in the solar neighbourhood. Methods: We compiled the data published in the
literature for young local associations. Using a realistic Galactic potential
we integrated the orbits for these associations and the Sco-Cen complex back in
time. Results: Combining these data with the spatial structure of the Local
Bubble and the spiral structure of the Galaxy, we propose a recent history of
star formation in the solar neighbourhood. We suggest that both the Sco-Cen
complex and young local associations originated as a result of the impact of
the inner spiral arm shock wave against a giant molecular cloud. The core of
the giant molecular cloud formed the Sco-Cen complex, and some small cloudlets
in a halo around the giant molecular cloud formed young local associations
several million years later. We also propose a supernova in young local
associations a few million years ago as the most likely candidate to have
reheated the Local Bubble to its present temperature.Comment: 27 pages, 13 figures, 14 tables. Accepted for publication in
Astronomy & Astrophysic
Transport coefficients of a massive pion gas
We review or main results concerning the transport coefficients of a light
meson gas, in particular we focus on the case of a massive pion gas. Leading
order results according to the chiral power-counting are presented for the DC
electrical conductivity, thermal conductivity, shear viscosity, and bulk
viscosity. We also comment on the possible correlation between the bulk
viscosity and the trace anomaly in QCD, as well as the relation between
unitarity and a minimum of the quotient near the phase transition.Comment: Talk given at the 5th International Conference on Quarks and Nuclear
Physics (QNP09), Beijing, September 21-26, 200
Chiral symmetry and mesons in hot and dense matter: recent developments
We review recent results on properties of the meson gas relevant for Heavy
Ion Collision and Nuclear Matter experiments, within the framework of chiral
lagrangians. In particular, we describe the temperature and density evolution
of the and poles and its connection with chiral symmetry
restoration, as well as the chemical nonequilibrated phase and transport
coefficients.Comment: Proceedings of the "Chiral10 International Workshop on Chiral
Symmetry in Hadrons and Nuclei", Valencia, Spain, 21-24 june 2010. 9 pages, 5
figures. AIP Proceedings styl
Interpolation of bilinear operators and compactness
The behavior of bilinear operators acting on interpolation of Banach spaces
for the method in relation to the compactness is analyzed. Similar
results of Lions-Peetre, Hayakawa and Person's compactness theorems are
obtained for the bilinear case and the method.Comment: This work was published at "Nonlinear Analysis: Theory, Methods and
Applications, Volume 73, Issue 2, 2010, Pages 526-537". Since there are some
gaps in the original proof of Theorem 4.3, Here we give a new proof. For
this, we change the Lemma 4.
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