1,124 research outputs found
Intermediate distance correlators in hot Yang-Mills theory
Lattice measurements of spatial correlation functions of the operators FF and
FF-dual in thermal SU(3) gauge theory have revealed a clear difference between
the two channels at "intermediate" distances, x ~ 1/(pi T). This is at odds
with the AdS/CFT limit which predicts the results to coincide. On the other
hand, an OPE analysis at short distances (x << 1/(pi T)) as well as effective
theory methods at long distances (x >> 1/(pi T)) suggest differences. Here we
study the situation at intermediate distances by determining the time-averaged
spatial correlators through a 2-loop computation. We do find unequal results,
however the numerical disparity is small. Apart from theoretical issues, a
future comparison of our results with time-averaged lattice measurements might
also be of phenomenological interest in that understanding the convergence of
the weak-coupling series at intermediate distances may bear on studies of the
thermal broadening of heavy quarkonium resonances.Comment: 31 page
Heavy Quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature
We calculate the heavy quarkonium energy levels and decay widths in a
quark-gluon plasma, whose temperature T and screening mass m_D satisfy the
hierarchy m alpha_s >> T >> m alpha_s^2 >> m_D (m being the heavy-quark mass),
at order m alpha_s^5. We first sequentially integrate out the scales m, m
alpha_s and T, and, next, we carry out the calculations in the resulting
effective theory using techniques of integration by regions. A collinear region
is identified, which contributes at this order. We also discuss the
implications of our results concerning heavy quarkonium suppression in heavy
ion collisions.Comment: 25 pages, 2 figure
On heavy-quarkonia suppression by final-state multiple scatterings in most central Au+Au collisions at RHIC
We study heavy-quarkonia suppression under final-state multiple scatterings
in most central Au~+~Au collisions at RHIC energy. We first calculate the
survival probability of a heavy quarkonium under multiple scattering in
Bjorken's expanding QGP at large . Then, we calculate the rapidity
dependence of the nuclear modification factor for heavy-quarkonia
production by considering final-state multiple scatterings in most central
Au~+~Au collisions in a simplified model. In our formula a constant is
also introduced to estimate the possible cold nuclear effects. By fitting the
data for production in most central Au + Au collisions at
~GeV at RHIC, we find that the transportation coefficient
\hat{q}_0\simeq(0.33-0.95)~\mbox{GeV}^2/fm, and, accordingly, the energy
density at is \epsilon_0\simeq(1.39-5.62)~\mbox{GeV}/\mbox{fm}^3 in
perturbative thermal QCD. A better understanding of cold nuclear effects is
essential for us to get a more accurate analysis. The small values of the
transportation coefficient in our estimate are in sharp contrast
with those obtained by the analysis of high- hadron spectra in Ref. [31].Comment: 20 pages, 8 figures, final version accepted for publication in
Nuclear Physics
Stability of 1+1 dimensional causal relativistic viscous hydrodynamics
The stability of the 1+1 dimensional solution of Israel-Stewart theory is
investigated. Firstly, the evolution of the temperature and the ratio of the
bulk pressure over the equilibrium pressure of the background is explored. Then
the stability with linear perturbations is studied by using the Lyapunov direct
method. It shows that the shear viscosity may weaken the instability induced by
the large peak of bulk viscosity around the phase transition temperature .Comment: 18 pages, 4 figures, 1 table; to be published in Nuclear Physics
Non-Markovian Dynamics of Spin Squeezing
We evaluate the spin squeezing dynamics of N independent spin-1/2 particles
with exchange symmetry. Each spin interacts with its own reservoir, and the
reservoirs are independently and identical. The spin squeezing parameter is
analytically calculated with different kinds of decoherence. The spin squeezing
property vanishes with evolution time under the Markovian decoherence. Whereas
coupled to the non-Markovian decoherence channels, the spin squeezing property
collapses and revives with time. As spin squeezing can be regarded as a witness
of multipartite entanglement, thus our scheme shows the collapse and revival of
multipartite entanglement under non-Markovian decoherence.Comment: 13 pages, 7 figure
Salivary flow rate, pH, and concentrations of calcium, phosphate, and sIgA in Brazilian pregnant and non-pregnant women
BACKGROUND: Studies on salivary variables and pregnancy in Latin America are scarce. This study aimed to compare salivary flow rate, pH, and concentrations of calcium, phosphate, and sIgA of unstimulated whole saliva in pregnant and non-pregnant Brazilians. METHODS: Cross-sectional study. Sample was composed by 22 pregnant and 22 non-pregnant women attending the Obstetrics and Gynecology Clinics, São Lucas Hospital, in Porto Alegre city, South region of Brazil. Unstimulated whole saliva was collected to determine salivary flow rate, pH, and biochemical composition. Data were analyzed by Student t test and ANCOVA (two-tailed α = 0.05). RESULTS: No difference was found for salivary flow rates and concentrations of total calcium and phosphate between pregnant and non-pregnant women (p > 0.05). Pregnant women had lower pH (6.7) than non-pregnant women (7.5) (p < 0.001), but higher sIgA level (118.9 mg/L) than the latter (90.1 mg/L) (p = 0.026). CONCLUSION: Some of the tested variables of unstimulated whole saliva were different between pregnant and non-pregnant Brazilians in this sample. Overall, the values of the tested salivary parameters were within the range of international references of normality
Higgs-Mediated Electric Dipole Moments in the MSSM: An Application to Baryogenesis and Higgs Searches
We perform a comprehensive study of the dominant two- and higher-loop
contributions to the Tl, neutron and muon electric dipole moments
induced by Higgs bosons, third-generation quarks and squarks, charginos and
gluinos in the Minimal Supersymmetric Standard Model (MSSM). We find that
strong correlations exist among the contributing CP-violating operators, for
large stop, gluino and chargino phases, and for a wide range of values of
and charged Higgs-boson masses, giving rise to large suppressions
of the Tl and neutron electric dipole moments below their present
experimental limits. Based on this observation, we discuss the constraints that
the non-observation of electric dipole moments imposes on the
radiatively-generated CP-violating Higgs sector and on the mechanism of
electroweak baryogenesis in the MSSM. We improve previously suggested benchmark
scenarios of maximal CP violation for analyzing direct searches of CP-violating
MSSM Higgs bosons at high-energy colliders, and stress the important
complementary r\^ole that a possible high-sensitivity measurement of the muon
electric dipole moment to the level of cm can play in such
analyses.Comment: 34 pages, one reference added, version as to appear in Nuclear
Physics
The impact of a major cluster merger on galaxy evolution in MACS\,J0025.4-1225
We present results of an extensive morphological, spectroscopic, and
photometric study of the galaxy population of MACS J0025.41225 (z=0.586), a
major cluster merger with clear segregation of dark and luminous matter, to
examine the impact of mergers on galaxy evolution. Based on 436 galaxy spectra
obtained with Keck DEIMOS, we identified 212 cluster members within 4 Mpc of
the cluster centre, and classified them using three spectroscopic types; we
find 111 absorption-line, 90 emission-line (including 23 e(a) and 11 e(b)), and
6 E+A galaxies. The fraction of absorption(emission)-line galaxies is a
monotonically increasing(decreasing) function of both projected galaxy density
and radial distance to the cluster center. More importantly, the 6 observed E+A
cluster members are all located between the dark-matter peaks of the cluster
and within ~0.3Mpc radius of the X-ray flux peak, unlike the E+A galaxies in
other intermediate-redshift clusters which are usually found to avoid the core
region. In addition, we use Hubble Space Telescope imaging to classify cluster
members according to morphological type. We find the global fraction of spiral
and lenticular galaxies in MACS J0025 to be among the highest observed to date
in clusters at z>0.5. The observed E+A galaxies are found to be of lenticular
type with Sersic indices of ~2, boosting the local fraction of S0 to 70 per
cent between the dark-matter peaks. Combing the results of our analysis of the
spatial distribution, morphology, and spectroscopic features of the galaxy
population, we propose that the starburst phase of these E+A galaxies was both
initiated and terminated during the first core-passage about 0.5--1Gyr ago, and
that their morphology has already been transformed into S0 due to ram pressure
and/or tidal forces near the cluster core. By contrast, ongoing starbursts are
observed predominantly in infalling galaxies, and thus appears to be unrelated
to the cluster merger.Comment: 18 pages, 17 figures, accepted by MNRA
Constraining warm dark matter with cosmic shear power spectra
We investigate potential constraints from cosmic shear on the dark matter
particle mass, assuming all dark matter is made up of light thermal relic
particles. Given the theoretical uncertainties involved in making cosmological
predictions in such warm dark matter scenarios we use analytical fits to linear
warm dark matter power spectra and compare (i) the halo model using a mass
function evaluated from these linear power spectra and (ii) an analytical fit
to the non-linear evolution of the linear power spectra. We optimistically
ignore the competing effect of baryons for this work. We find approach (ii) to
be conservative compared to approach (i). We evaluate cosmological constraints
using these methods, marginalising over four other cosmological parameters.
Using the more conservative method we find that a Euclid-like weak lensing
survey together with constraints from the Planck cosmic microwave background
mission primary anisotropies could achieve a lower limit on the particle mass
of 2.5 keV.Comment: 26 pages, 9 figures, minor changes to match the version accepted for
publication in JCA
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