202 research outputs found
Mesonic screening masses at high temperature and finite density
We compute the first perturbative correction to the static correlation
lengths of light quark bilinears in hot QCD with finite quark chemical
potentials. The correction is small and positive, with mu-dependence depending
on the relative sign of chemical potentials and the number of dynamical
flavors. The computation is carried out using a three-dimensional effective
theory for the lowest fermionic Matsubara mode. We also compute the full
correlator in free theory and find a rather complicated general mu-dependence
at shorter distances. Finally, rough comparisons with lattice simulations are
discussed.Comment: 24 pages, 5 figures, JHEP style. Minor corrections and
clarifications, version to appear in JHE
Four-loop pressure of massless O(N) scalar field theory
Inspired by the corresponding problem in QCD, we determine the pressure of
massless O(N) scalar field theory up to order g^6 in the weak-coupling
expansion, where g^2 denotes the quartic coupling constant. This necessitates
the computation of all 4-loop vacuum graphs at a finite temperature: by making
use of methods developed by Arnold and Zhai at 3-loop level, we demonstrate
that this task is manageable at least if one restricts to computing the
logarithmic terms analytically, while handling the ``constant'' 4-loop
contributions numerically. We also inspect the numerical convergence of the
weak-coupling expansion after the inclusion of the new terms. Finally, we point
out that while the present computation introduces strategies that should be
helpful for the full 4-loop computation on the QCD-side, it also highlights the
need to develop novel computational techniques, in order to be able to complete
this formidable task in a systematic fashion.Comment: 34 page
The diagonal and off-diagonal quark number susceptibility of high temperature and finite density QCD
We study the quark number susceptibility of the hot quark-gluon plasma at
zero and non-zero quark number density, using lattice Monte Carlo simulations
of an effective theory of QCD, electrostatic QCD (EQCD). Analytic continuation
is used to obtain results at non-zero quark chemical potential. We measure both
flavor singlet (diagonal) and non-singlet (off-diagonal) quark number
susceptibilities. The diagonal susceptibility approaches the perturbative
result above 20T_c, but below that temperature we observe significant
deviations. The results agree well with 4d lattice data down to temperatures
2T_c. The off-diagonal susceptibility is more prone to statistical and
systematic errors, but the results are consistent with perturbation theory
already at 10T_c.Comment: 21 pages, 8 figures. Published version, references added, conclusions
unchange
Energetic di-leptons from the Quark Gluon Plasma
In this paper we study the production of energetic di-leptons. We calculate
the rate for 2 2 processes. The log term is obtained analytically and the
constant term is calculated numerically. When the photon mass is of the order
of the thermal quark mass, the result is insensitive to the photon mass and the
soft logarithmic divergence is regulated by the thermal quark mass, exactly as
in the case of real photons. We also consider the production of thermal
Drell-Yan dileptons (thermal quark and antiquark pairs produced by virtual
photons) and calculate the rate systematically in the context of the hard
thermal loop effective theory. We obtain analytic and numerical results. We
compare our results with those of previous calculations.Comment: 12 pages, 10 figure
The fermion mass at next-to-leading order in the HTL effective theory
The calculation of the real part of a quasi-particle dispersion relation at
next-to-leading order in the hard thermal loop effective theory is a very
difficult problem. Even though the hard thermal loop effective theory is almost
20 years old, there is only one next-to-leading order calculation of the real
part of a quasi-particle dispersion relation in the literature. In this paper,
we calculate the fermion mass in QED and QCD at next-to-leading order. For QED
the result is M=eT/sqrt{8} * [1-(1.427 \pm 0.02)e/4pi] and for QCD with N_f=2
and N_c=3 we obtain M=gT/sqrt{6} * [1+(1.867 \pm 0.02)g/4pi].Comment: 9 pages, 5 figure
Weinberg-Salam model at finite temperature and density
We present a new gauge fixing condition for the Weinberg-Salam electro-weak
theory at finite temperature and density.
After spontaneous symmetry breaking occurs, every unphysical term in the
Lagrangian is eliminated with our gauge fixing condition. A new and simple
Lagrangian can be obtained where we can identify the propagators and vertices.
Some consequences are discussed, as the new gauge dependent masses of the gauge
fields and the new Faddeev-Popov Lagrangian. After obtaining the quadratic
terms, we calculate exactly the 1-loop effective potential identifying the
contribution of every particular field.Comment: 4 pages, no figures. New references added. Typo correcte
Evaluation of Novel Imidazotetrazine Analogues Designed to Overcome Temozolomide Resistance and Glioblastoma Regrowth
The cellular responses to two new temozolomide (TMZ) analogues, DP68 and DP86, acting against glioblastoma multi- forme (GBM) cell lines and primary culture models are reported. Dose–response analysis of cultured GBM cells revealed that DP68 is more potent than DP86 and TMZ and that DP68 was effective even in cell lines resistant to TMZ. On the basis of a serial neurosphere assay, DP68 inhibits repop- ulation of these cultures at low concentrations. The efficacy of these compounds was independent of MGMT and MMR func- tions. DP68-induced interstrand DNA cross-links were dem- onstrated with H2O2-treated cells. Furthermore, DP68 induced a distinct cell–cycle arrest with accumulation of cells in S phase that is not observed for TMZ. Consistent with this biologic response, DP68 induces a strong DNA damage response, including phosphorylation of ATM, Chk1 and Chk2 kinases, KAP1, and histone variant H2AX. Suppression of FANCD2 expression or ATR expression/kinase activity enhanced anti- glioblastoma effects of DP68. Initial pharmacokinetic analysis revealed rapid elimination of these drugs from serum. Collec- tively, these data demonstrate that DP68 is a novel and potent antiglioblastoma compound that circumvents TMZ resistance, likely as a result of its independence from MGMT and mismatch repair and its capacity to cross-link strands of DN
Systemic Inflammation Induced Changes in Protein Expression of ABC Transporters and Ionotropic Glutamate Receptor Subunit 1 in the Cerebral Cortex of Familial Alzheimer`s Disease Mouse Model
Alzheimer's disease (AD) is an incurable disease, with complex pathophysiology and a myriad of proteins involved in its development. In this study, we applied quantitative targeted absolute proteomic analysis for investigation of changes in potential AD drug targets, biomarkers, and transporters in cerebral cortices of lipopolysaccharide (LPS)-induced neuroinflammation mouse model, familial AD mice (APdE9) with and without LPS treatment as compared to age-matched wild type (WT) mice. The ABCB1, ABCG2 and GluN1 protein expression ratios between LPS treated APdE9 and WT control mice were 0.58 (95% CI 0.44-0.72), 0.65 (95% CI 0.53-0.77) and 0.61 (95% CI 0.52-0.69), respectively. The protein expression levels of other proteins such as MGLL, COX-2, CytC, ABCC1, ABCC4, SLC2A1 and SLC7A5 did not differ between the study groups. Overall, the study revealed that systemic inflammation can alter ABCB1 and ABCG2 protein expression in brain in AD, which can affect intra-brain drug distribution and play a role in AD development. Moreover, the inflammatory insult caused by peripheral infection in AD may be important factor triggering changes in GluN1 protein expression. However, more studies need to be performed in order to confirm these findings. The quantitative information about the expression of selected proteins provides important knowledge, which may help in the optimal use of the mouse models in AD drug development and better translation of preclinical data to humans. (c) 2021 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.Peer reviewe
Three-loop matching coefficients for hot QCD: Reduction and gauge independence
We perform an integral reduction for the 3-loop effective gauge coupling and
screening mass of QCD at high temperatures, defined as matching coefficients
appearing in the dimensionally reduced effective field theory (EQCD).
Expressing both parameters in terms of a set master (sum-) integrals, we show
explicit gauge parameter independence. The lack of suitable methods for solving
the comparatively large number of master integrals forbids the complete
evaluation at the moment. Taking one generic class of masters as an example, we
highlight the calculational techniques involved. The full result would allow to
improve on one of the classic probes for the convergence of the weak-coupling
expansion at high temperatures, namely the comparison of full and effective
theory determinations of the spatial string tension. Furthermore, the full
result would also allow to determine one new contribution of order O(g**7) to
the pressure of hot QCD.Comment: 19 pages, 2 figures. v2: new Section 6 discussing applications, to
match journal versio
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
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