967 research outputs found
CP violation in the effective action of the Standard Model
Following a suggestion by Smit, the CP odd terms of the effective action of
the Standard Model, obtained by integration of quarks and leptons, are computed
to sixth order within a strict covariant derivative expansion approach. No
other approximations are made. The final result so derived includes all
Standard Model gauge fields and Higgs. Remarkably, at the order considered in
this work, all parity violating contributions turn out to be zero. Non
vanishing CP violating terms are obtained in the C-odd P-even sector. These are
several orders of magnitude larger than perturbative estimates. Various
unexpected regularities in the final result are noted.Comment: 32 pages, no figures. Section added. To appear in JHE
Pairing, Charge, and Spin Correlations in the Three-Band Hubbard Model
Using the Constrained Path Monte Carlo (CPMC) method, we simulated the
two-dimensional, three-band Hubbard model to study pairing, charge, and spin
correlations as a function of electron and hole doping and the Coulomb
repulsion between charges on neighboring Cu and O lattice sites. As a
function of distance, both the -wave and extended s-wave pairing
correlations decayed quickly. In the charge-transfer regime, increasing
decreased the long-range part of the correlation functions in both
channels, while in the mixed-valent regime, it increased the long-range part of
the s-wave behavior but decreased that of the d-wave behavior. Still the d-wave
behavior dominated. At a given doping, increasing increased the
spin-spin correlations in the charge-transfer regime but decreased them in the
mixed-valent regime. Also increasing suppressed the charge-charge
correlations between neighboring Cu and O sites. Electron and hole doping away
from half-filling was accompanied by a rapid suppression of anti-ferromagnetic
correlations.Comment: Revtex, 8 pages with 15 figure
Superfluidity vs Bose-Einstein condensation in a Bose gas with disorder
We investigate the phenomenon of Bose-Einstein condensation and superfluidity
in a Bose gas at zero temperature with disorder. By using the Diffusion
Monte-Carlo method we calculate the superfluid and the condensate fraction of
the system as a function of density and strength of disorder. In the regime of
weak disorder we find agreement with the analytical results obtained within the
Bogoliubov model. For strong disorder the system enters an unusual regime where
the superfluid fraction is smaller than the condensate fraction.Comment: 4 pages, 4 Postscript figure
Experimental preparation of Werner state via spontaneous parametric down-conversion
We present an experiment of preparing Werner state via spontaneous parametric
down-conversion and controlled decoherence of photons in this paper. In this
experiment two independent BBO (beta-barium borate) crystals are used to
produce down-conversion light beams, which are mixed to prepare Werner state.Comment: 6 pages, 4 figures and 2 table
Massive quark propagator and competition between chiral and diquark condensate
The Green-function approach has been extended to the moderate baryon density
region in the framework of an extended Nambu--Jona-Lasinio model, and the
thermodynamic potential with both chiral and diquark condensates has been
evaluated by using the massive quark propagator. The phase structure along the
chemical potential direction has been investigated and the strong competition
between the chiral and diquark condensate has been analyzed by investigating
the influence of the diquark condensate on the sharp Fermi surface. The
influence of the diquark condensate on the quark properties has been
investigated, even though the quarks in the color breaking phase are very
different from that in the chiral breaking phase, the difference between quarks
in different colors is very small.Comment: Revtex, 34 pages, 7 figures, section V revised, accepted by PR
Near-Maximal Mixing of Scalar Gluonium and Quark Mesons: A Gaussian Sum-Rule Analysis
Gaussian QCD sum-rules are ideally suited to the study of mixed states of
gluonium (glueballs) and quark () mesons because of their capability
to resolve widely-separated states of comparable strength. The analysis of the
Gaussian QCD sum-rules (GSRs) for all possible two-point correlation functions
of gluonic and non-strange () quark scalar () currents is
discussed. For the non-diagonal sum-rule of gluonic and currents we
show that perturbative and gluon condensate contributions are chirally
suppressed compared to non-perturbative effects of the quark condensate, mixed
condensate, and instantons, implying that the mixing of quark mesons and
gluonium is of non-perturbative origin. The independent predictions of the
masses and relative coupling strengths from the non-diagonal and the two
diagonal GSRs are remarkably consistent with a scenario of two states with
masses of approximately 1 GeV and 1.4 GeV that couple to significant mixtures
of quark and gluonic currents. The mixing is nearly maximal with the heavier
mixed state having a slightly larger coupling to gluonic currents than the
lighter state.Comment: Updated version contains extended analysis and revised analysis
methods. 21 pages, 14 figure
A statistical interpretation of the correlation between intermediate mass fragment multiplicity and transverse energy
Multifragment emission following Xe+Au collisions at 30, 40, 50 and 60 AMeV
has been studied with multidetector systems covering nearly 4-pi in solid
angle. The correlations of both the intermediate mass fragment and light
charged particle multiplicities with the transverse energy are explored. A
comparison is made with results from a similar system, Xe+Bi at 28 AMeV. The
experimental trends are compared to statistical model predictions.Comment: 7 pages, submitted to Phys. Rev.
Constraining spacetime torsion with LAGEOS
We compute the corrections to the orbital Lense-Thirring effect (or
frame-dragging) in the presence of spacetime torsion. We derive the equations
of motion of a test body in the gravitational field of a rotating axisymmetric
massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi.
We calculate the secular variations of the longitudes of the node and of the
pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be
used to constrain torsion parameters. We report the experimental constraints
obtained using both the nodes and perigee measurements of the orbital
Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB)
complementary frame-dragging and torsion experiments, since they constrain
three different combinations of torsion parameters
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