2,972 research outputs found
Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model
We consider the three flavor Nambu-Jona-Lasinio model with the 't Hooft
interaction incorporating the U(1)_A anomaly. In order to set the coupling
strength of the 't Hooft term, we employ the topological susceptibility
instead of the eta' meson mass. The value for is taken from lattice
simulations. We also calculate at finite temperature within the model.
Comparing it with the lattice data, we extract information about the behavior
of the U(1)_A anomaly at finite temperature. We conclude that within the
present framework, the effective restoration of the U(1)_A symmetry does not
necessarily take place even at high temperature where the chiral symmetry is
restored.Comment: 9 pages, 14 figures, to be published in Phys.Rev.
Electronic charges and electric potential at LaAlO3/SrTiO3 interfaces studied by core-level photoemission spectroscopy
We studied LaAlO3/SrTiO3 interfaces for varying LaAlO3 thickness by
core-level photoemission spectroscopy. In Ti 2p spectra for conducting "n-type"
interfaces, Ti3+ signals appeared, which were absent for insulating "p-type"
interfaces. The Ti3+ signals increased with LaAlO3 thickness, but started well
below the critical thickness of 4 unit cells for metallic transport. Core-level
shifts with LaAlO3 thickness were much smaller than predicted by the polar
catastrophe model. We attribute these observations to surface
defects/adsorbates providing charges to the interface even below the critical
thickness
Earthquake fault rock indicating a coupled lubrication mechanism
International audienceA pseudotachylyte bounded by a carbonate-matrix implosion breccia was found at a fossilized out-of-sequence thrust in the Shimanto accretionary complex, Japan. This occurrence resulted from the following events: first implosion of host rock due to interstitial fluid pressure increase and asymmetric fracturing; second, Ca-Fe-Mg carbonate precipitation; and third, frictional melting. The rock-record suggests that these events took place in a single seismogenic slip event. Resulting from abrupt drop in fluid pressure after implosion, hydro-fracturing and fluid escape, recovered high effective friction promoted melting during fault movement. Coexistence of fluid implosion breccia and pseudotachylyte has never been reported from continental pseudotachylytes, but might be characteristic from hydrous seismogenic faults in subduction zones
Thermodynamic evolution of cosmological baryonic gas: I. Influence of non-equipartition processes
Using N-body/hydrodynamic simulations, the influence of non-equipartition
processes on the thermal and dynamical properties of cosmological baryonic gas
is investigated. We focus on a possible departure from equilibrium between
electrons, ions and neutral atoms in low temperature (10^4-10^6 K) and weakly
ionized regions of the intergalactic medium. The simulations compute the energy
exchanges between ions, neutrals and electrons, without assuming thermal
equilibrium. They include gravitation, shock heating and cooling processes, and
follow self-consistently the chemical evolution of a primordial composition
hydrogen-helium plasma without assuming collisional ionization equilibrium. At
high redshift, a significant fraction of the intergalactic medium is found to
be warmer and weakly ionized in simulations with non-equipartition processes
than in simulations in which the cosmological plasma is considered to be in
thermodynamic equilibrium. With a semi-analytical study of the out of
equilibrium regions we show that, during the formation of cosmic structures,
departure from equilibrium in accreted plasma results from the competition
between the atomic cooling processes and the elastic processes between heavy
particles and electrons. Our numerical results are in agreement with this
semi-analytical model. Therefore, since baryonic matter with temperatures
around 10^4 K is a reservoir for galaxy formation, non-equipartition processes
are expected to modify the properties of the objects formed.Comment: 15 pages, 16 figures. Accepted for publication in A&A. For a version
with high-resolution figures, see
http://www.raunvis.hi.is/~courty/series.htm
Chemical potential shift induced by double-exchange and polaronic effects in Nd_{1-x}Sr_xMnO_3
We have studied the chemical potential shift as a function of temperature in
NdSrMnO (NSMO) by measurements of core-level photoemission
spectra. For ferromagnetic samples ( and 0.45), we observed an unusually
large upward chemical potential shift with decreasing temperature in the
low-temperature region of the ferromagnetic metallic (FM) phase. This can be
explained by the double-exchange (DE) mechanism if the band is split by
dynamical/local Jahn-Teller effect. The shift was suppressed near the Curie
temperature (), which we attribute to the crossover from the DE to
lattice-polaron regimes.Comment: 5 pages, 6 figure
Non-Thermal Emission from Relativistic Electrons in Clusters of Galaxies: A Merger Shock Acceleration Model
We have investigated evolution of non-thermal emission from relativistic
electrons accelerated at around the shock fronts during merger of clusters of
galaxies. We estimate synchrotron radio emission and inverse Compton scattering
of cosmic microwave background photons from extreme ultraviolet (EUV) to hard
X-ray range. The hard X-ray emission is most luminous in the later stage of
merger. Both hard X-ray and radio emissions are luminous only while signatures
of merging events are clearly seen in thermal intracluster medium (ICM). On the
other hand, EUV radiation is still luminous after the system has relaxed.
Propagation of shock waves and bulk-flow motion of ICM play crucial roles to
extend radio halos. In the contracting phase, radio halos are located at the
hot region of ICM, or between two substructures. In the expanding phase, on the
other hand, radio halos are located between two ICM hot regions and shows
rather diffuse distribution.Comment: 19 pages, 5 figures, accepted for publication in Ap
Self-Energy Effects on the Low- to High-Energy Electronic Structure of SrVO3
The correlated electronic structure of SrVO3 has been investigated by
angle-resolved photoemission spectroscopy using in-situ prepared thin films.
Pronounced features of band renormalization have been observed: a sharp kink
~60 meV below the Fermi level (EF) and a broad so-called "high-energy kink"
~0.3 eV below EF as in the high-Tc cuprates although SrVO3 does not show
magnetic fluctuations. We have deduced the self-energy in a wide energy range
by applying the Kramers-Kronig relation to the observed spectra. The obtained
self-energy clearly shows a large energy scale of ~0.7 eV which is attributed
to electron-electron interaction and gives rise to the ~0.3 eV "kink" in the
band dispersion as well as the incoherent peak ~1.5eV below EF. The present
analysis enables us to obtain consistent picture both for the incoherent
spectra and the band renormalization.Comment: 5 pages, 3 figure
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