1,139 research outputs found
The Lattice Free Energy with Overlap Fermions: A Two-Loop Result
We calculate the 2-loop partition function of QCD on the lattice, using the
Wilson formulation for gluons and the overlap-Dirac operator for fermions.
Direct by-products of our result are the 2-loop free energy and average
plaquette. Our calculation serves also as a prototype for further higher loop
calculations in the overlap formalism. We present our results as a function of
a free parameter entering the overlap action; the dependence on the
number of colors and fermionic flavors is shown explicitly.Comment: 10 pages, 5 figures. Final version to appear in Physical Review D. A
missing overall factor was inserted in Eq. 12; it affects also Eq. 1
Robust probabilistic-constrained optimization for IRS-aided MISO communication systems
Taking into account imperfect channel state information, this letter formulates and solves a joint active/passive beamforming optimization problem in multiple-input single-output systems with the support of an intelligent reflecting surface. In particular, we introduce an optimization problem to minimize the total transmit power subject to maintaining the users' signal-to-interference-plus-noise-ratio coverage probability above a predefined target. Due to the presence of probabilistic constraints, the proposed optimization problem is non-convex. To circumvent this issue, we first recast the proposed problem in a convex form by adopting the Bernstein-type inequality, and we then introduce a converging alternating optimization approach to iteratively find the active/passive beamforming vectors. In particular, the transformed robust optimization problem can be effectively solved by using standard interior-point methods. Numerical results demonstrate the effectiveness of jointly optimizing the active/passive beamforming vectors
3-d Lattice QCD Free Energy to Four Loops
We compute the expansion of the 3-d Lattice QCD free energy to four loop
order by means of Numerical Stochastic Perturbation Theory. The first and
second order are already known and are correctly reproduced. The third and
fourth order coefficients are new results. The known logarithmic divergence in
the fourth order is correctly identified. We comment on the relevance of our
computation in the context of dimensionally reduced finite temperature QCD.Comment: 8 pages, 3 figures, latex typeset with JHEP3.cl
Infrared Renormalons and Finite Volume
We analyze the perturbative expansion of a condensate in the O(N) non-linear
sigma model for large N on a two dimensional finite lattice. On an infinite
volume this expansion is affected by an infrared renormalon. We extrapolate
this analysis to the case of the gluon condensate of Yang-Mills theory and
argue that infrared renormalons can be detected by performing perturbative
studies even on relatively small lattices.Comment: LaTeX file, 6 figures in postscrip
How to produce cheap and easy custom-made sterilizable filtering facepiece 2/3 masks for healthcare providers during pandemic COVID-19 emergency
On January 8, 2020, a novel coronavirus was officially announced as the causative pathogen of coronavirus disease (COVID-19) by the Chinese Center for Disease Control and Prevention.On February 26, COVID-19 has been recognized in 34 countries, with a total of 80,239 laboratory-confirmed patients and 2700 deaths.Protecting healthcare workers from infectious hazards is paramount to ensuring their safety in delivering health care.In addition, being able to protect healthcare workers, constituting the front-line response against high-threat respiratory pathogens, such as severe acute respiratory syndrome coronavirus 2, is important for reducing secondary transmission in healthcare-associated outbreaks.Authors present a simple, reliable, and cheap protocol to produce a custom-made sterilizable filtering facepiece 2/3 masks for healthcare providers during pandemic COVID-19 emergency
Pressure to order in -theory at weak coupling
We calculate the pressure of massless -theory to order
at weak coupling. The contributions to the pressure arise from the hard
momentum scale of order and the soft momentum scale of order .
Effective field theory methods and dimensional reduction are used to separate
the contributions from the two momentum scales: The hard contribution can be
calculated as a power series in using naive perturbation theory with bare
propagators. The soft contribution can be calculated using an effective theory
in three dimensions, whose coefficients are power series in . This
contribution is a power series in starting at order . The calculation
of the hard part to order involves a complicated four-loop sum-integral
that was recently calculated by Gynther, Laine, Schr\"oder, Torrero, and
Vuorinen. The calculation of the soft part requires calculating the mass
parameter in the effective theory to order and the evaluation of
five-loop vacuum diagrams in three dimensions. This gives the free energy
correct up to order . The coefficients of the effective theory satisfy a
set of renormalization group equations that can be used to sum up leading and
subleading logarithms of . We use the solutions to these equations to
obtain a result for the free energy which is correct to order .
Finally, we investigate the convergence of the perturbative series.Comment: 29 pages and 12 figs. New version: we have pushed the calculations to
g^8*log(g) using the renormalization group to sum up log(g) from higher
orders. Published in JHE
Large-order NSPT for lattice gauge theories with fermions:the plaquette in massless QCD
Numerical Stochastic Perturbation Theory (NSPT) allows for perturbative
computations in quantum field theory. We present an implementation of NSPT that
yields results for high orders in the perturbative expansion of lattice gauge
theories coupled to fermions. The zero-momentum mode is removed by imposing
twisted boundary conditions; in turn, twisted boundary conditions require us to
introduce a smell degree of freedom in order to include fermions in the
fundamental representation. As a first application, we compute the critical
mass of two flavours of Wilson fermions up to order in a
gauge theory. We also implement, for the first time,
staggered fermions in NSPT. The residual chiral symmetry of staggered fermions
protects the theory from an additive mass renormalisation. We compute the
perturbative expansion of the plaquette with two flavours of massless staggered
fermions up to order in a gauge theory, and
investigate the renormalon behaviour of such series. We are able to subtract
the power divergence in the Operator Product Expansion (OPE) for the plaquette
and estimate the gluon condensate in massless QCD. Our results confirm that
NSPT provides a viable way to probe systematically the asymptotic behaviour of
perturbative series in QCD and, eventually, gauge theories with fermions in
higher representations.Comment: 49 pages, 28 figures. Revised version, to be published in EPJC. Some
references added, typos corrected, and improved discussion on finite-volume
effect
Fotemustine plus etoposide, cytarabine and melphalan (FEAM) as a new conditioning regimen for lymphoma patients undergoing auto-SCT: A multicenter feasibility study
BEAM is a widely used conditioning regimen for relapsed/refractory lymphoma patients undergoing auto-SCT. We conducted a multicenter study with an alternative regimen (fotemustine plus etoposide, cytarabine and melphalan (FEAM)) in which BCNU was substituted by the chloroethylnitrosourea fotemustine (FTM). Eighty-four patients with relapsed/refractory Hodgkin's (n20) and non-Hodgkin's lymphoma (n64) were conditioned with a FEAM regimen (FTM 150 mg/m 2 on days -7, -6, etoposide 200 mg/m 2 and cytarabine 400 mg/m 2 on days -5, -4, -3, -2 and melphalan 140 mg/m 2 on day -1). Patients were evaluated for toxicity and engraftment parameters. Median times to neutrophil (500 à 10 9 /l) and plt (20 000 à 10 9 /l) engraftment were 11 and 13 days, respectively. Grade 3 mucositis occurred in 19 patients (23%), while G3 nausea/vomiting and G3 diarrhea were observed in 13 (15%) and 6 (7%) patients, respectively. No severe hepatic, renal or pulmonary toxicity was detected. Seven patients (7%) experienced G4 mucositis, while no other G4 toxicities or unexpected adverse events of any grade were recorded. Transplant-related mortality was 2.4%. We conclude that a FEAM regimen is feasible and safe. Although toxicity and engraftment times compared favorably with BEAM, longer follow-up is needed to evaluate fully its efficacy and long-term safety. © 2010 Macmillan Publishers Limited All rights reserved
Plaquette expectation value and gluon condensate in three dimensions
In three dimensions, the gluon condensate of pure SU(3) gauge theory has
ultraviolet divergences up to 4-loop level only. By subtracting the
corresponding terms from lattice measurements of the plaquette expectation
value and extrapolating to the continuum limit, we extract the finite part of
the gluon condensate in lattice regularization. Through a change of
regularization scheme to MSbar and (inverse) dimensional reduction, this result
would determine the first non-perturbative coefficient in the weak-coupling
expansion of hot QCD pressure.Comment: 11 page
Resveratrol via sirtuin-1 downregulates RE1-silencing transcription factor (REST) expression preventing PCB-95-induced neuronal cell death
Resveratrol (3,5,4'-trihydroxystilbene) (RSV), a polyphenol widely present in plants, exerts a neuroprotective function in several neurological conditions; it is an activator of class III histone deacetylase sirtuin1 (SIRT1), a crucial regulator in the pathophysiology of neurodegenerative diseases. By contrast, the RE1-silencing transcription factor (REST) is involved in the neurotoxic effects following exposure to polychlorinated biphenyl (PCB) mixture A1254. The present study investigated the effects of RSV-induced activation of SIRT1 on REST expression in SH-SY5Y cells. Further, we investigated the possible relationship between the non-dioxin-like (NDL) PCB-95 and REST through SIRT1 to regulate neuronal death in rat cortical neurons. Our results revealed that RSV significantly decreased REST gene and protein levels in a dose- and time-dependent manner. Interestingly, overexpression of SIRT1 reduced REST expression, whereas EX-527, an inhibitor of SIRT1, increased REST expression and blocked RSV-induced REST downregulation. These results suggest that RSV downregulates REST through SIRT1. In addition, RSV enhanced activator protein 1 (AP-1) transcription factor c-Jun expression and its binding to the REST promoter gene. Indeed, c-Jun knockdown reverted RSV-induced REST downregulation. Intriguingly, in SH-SY5Y cells and rat cortical neurons the NDL PCB-95 induced necrotic cell death in a concentration-dependent manner by increasing REST mRNA and protein expression. In addition, SIRT1 knockdown blocked RSV-induced neuroprotection in rat cortical neurons treated with PCB-95. Collectively, these results indicate that RSV via SIRT1 activates c-Jun, thereby reducing REST expression in SH-SY5Y cells under physiological conditions and blocks PCB-95-induced neuronal cell death by activating the same SIRT1/c-Jun/REST pathway
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