1,721,256 research outputs found
Thermodynamics of two flavor QCD from imaginary chemical potentials
No full textWe study QCD thermodynamics in presence of two independent imaginary chemical
potentials coupled to two degenerate flavors of staggered quarks. Analytic
continuation is used to determine non-linear susceptibilities, to test the
Hadron Resonance Gas (HRG) model below the zero density critical temperature,
Tc, and to determine the average phase factor of the fermion determinant.
Deviations from HRG predictions, of the order of a few percent, are clearly
visible for temperatures T > 0.95 Tc. The determination of non-linear
susceptibilities, using different interpolating functions for analytic
continuation, gives consistent results and in agreement with Taylor expansion
computations, apart from some systematic effects at or right above Tc. Results
for the average phase factor are compared with the predictions of Chiral
Perturbation Theory; below Tc we are able to distinguish the contribution of
different hadron states, which is positive (i.e. tends to mitigate the sign
problem) in the case of baryons
Light-quark contribution to the leading hadronic vacuum polarization term of the muon g-2 from twisted-mass fermions
No full textWe present a lattice calculation of the leading hadronic vacuum polarization (HVP) contribution of the light u- and d-quarks to the anomalous magnetic moment of the muon, aμHVP(ud), adopting the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf=2+1+1 dynamical quarks at three values of the lattice spacing (a≃0.062,0.082,0.089 fm) with pion masses in the range Mπ≃210-450 MeV. Thanks to several lattices at fixed values of the light-quark mass and scale but with different sizes we perform a careful investigation of finite-volume effects (FVEs), which represent one of main source of uncertainty in modern lattice calculations of aμHVP(ud). In order to remove FVEs we develop an analytic representation of the vector correlator, which describes the lattice data for time distances larger than ≃0.2 fm. The representation is based on quark-hadron duality at small and intermediate time distances and on the two-pion contributions in a finite box at larger time distances. After removing FVEs we extrapolate the corrected lattice data to the physical pion point and to the continuum limit taking into account the chiral logs predicted by Chiral Perturbation Theory (ChPT). We obtain aμHVP(ud)=619.0(17.8)×10-10. Adding the contribution of strange and charm quarks, obtained by ETMC, and an estimate of the isospin-breaking corrections and quark-disconnected diagrams from the literature we get aμHVP(udsc)=683(19)×10-10, which is consistent with recent results based on dispersive analyses of the experimental cross section data for e+e- annihilation into hadrons. Using our analytic representation of the vector correlator, taken at the physical pion mass in the continuum and infinite volume limits, we provide the first eleven moments of the polarization function and we compare them with recent results of the dispersive analysis of the π+π- channels. We estimate also the light-quark contribution to the missing part of aμHVP not covered in the MUonE experiment
Practical approach to diastolic dysfunction in light of the new guidelines and clinical applications in the operating room and in the intensive care
Full text linkThere is growing evidence both in the perioperative period and in the field of intensive care (ICU) on the association between left ventricular diastolic dysfunction (LVDD) and worse outcomes in patients. The recent American Society of Echocardiography and European Association of Cardiovascular Imaging joint recommendations have tried to simplify the diagnosis and the grading of LVDD. However, both an often unknown pre-morbid LV diastolic function and the presence of several confounders—i.e., use of vasopressors, positive pressure ventilation, volume loading—make the proposed parameters difficult to interpret, especially in the ICU. Among the proposed parameters for diagnosis and grading of LVDD, the two tissue Doppler imaging-derived variables e′ and E/e′ seem most reliable. However, these are not devoid of limitations. In the present review, we aim at rationalizing the applicability of the recent recommendations to the perioperative and ICU areas, discussing the clinical meaning and echocardiographic findings of different grades of LVDD, describing the impact of LVDD on patients’ outcomes and providing some hints on the management of patients with LVDD. © 2018, The Author(s)
The order of the Roberge-Weiss endpoint (finite size transition) in QCD
No full textWe consider the endpoint of the Roberge-Weiss (RW) first order transition
line present for imaginary baryon chemical potentials. We remark that it
coincides with the finite size transition relevant in the context of large
QCD and study its order in the theory with two degenerate flavors. The RW
endpoint is first order in the limit of large and small quark masses, while it
weakens for intermediate masses where it is likely in the Ising 3d universality
class. Phenomenological implications and further speculations about the QCD
phase diagram are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The critical line of two-flavor QCD at finite isospin or baryon densities from imaginary chemical potentials
No full textWe determine the (pseudo)critical lines of QCD with two degenerate staggered
fermions at nonzero temperature and quark or isospin density, in the region of
imaginary chemical potentials; analytic continuation is then used to prolongate
to the region of real chemical potentials. We obtain an accurate determination
of the curvatures at zero chemical potential, quantifying the deviation between
the case of finite quark and of finite isospin chemical potential. Deviations
from a quadratic dependence of the pseudocritical lines on the chemical
potential are clearly seen in both cases: we try different extrapolations and,
for the case of nonzero isospin chemical potential, confront them with the
results of direct Monte Carlo simulations. Finally we find that, as for the
finite quark density case, an imaginary isospin chemical potential can
strengthen the transition till turning it into strong first order
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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