1,757 research outputs found
The Schr\"odinger-Langevin equation with and without thermal fluctuations
The Schr\"odinger-Langevin (SL) equation is considered as an effective open
quantum system formalism suitable for phenomenological applications involving a
quantum subsystem interacting with a thermal bath. We focus on two open issues
relative to its solutions: the stationarity of the excited states of the
non-interacting subsystem when one considers the dissipation only and the
thermal relaxation toward asymptotic distributions with the additional
stochastic term. We first show that a proper application of the Madelung/polar
transformation of the wave function leads to a non zero damping of the excited
states of the quantum subsystem. We then study analytically and numerically the
SL equation ability to bring a quantum subsystem to the thermal equilibrium of
statistical mechanics. To do so, concepts about statistical mixed states and
quantum noises are discussed and a detailed analysis is carried with two kinds
of noise and potential. We show that within our assumptions the use of the SL
equation as an effective open quantum system formalism is possible and discuss
some of its limitations.Comment: 38 pages, 31 figure
Semi-classical approach to suppression in high energy heavy-ion collisions
We study the heavy quark/antiquark pair dynamics in strongly-coupled quark
gluon plasma. A semi-classical approach, based on the Wigner distribution and
Langevin dynamics, is applied to a color screened pair, in a
hydrodynamically cooling fireball, to evaluate the total suppression
at both RHIC and LHC energies. Although its limitation is observed, this
approach results to a suppression of around 0.30 at RHIC and 0.25 at
LHC.Comment: 4 pages, 6 figures, Proceeding for International Conference on
Strangeness in Quark Matter 2013 (SQM 2013) at Birmingha
The QCD transition temperature: results with physical masses in the continuum limit
The transition temperature () of QCD is determined by Symanzik improved
gauge and stout-link improved staggered fermionic lattice simulations. We use
physical masses both for the light quarks () and for the strange quark
(). Four sets of lattice spacings (=4,6,8 and 10) were used to carry
out a continuum extrapolation. It turned out that only =6,8 and 10 can be
used for a controlled extrapolation, =4 is out of the scaling region.
Since the QCD transition is a non-singular cross-over there is no unique .
Thus, different observables lead to different numerical values even in
the continuum and thermodynamic limit. The peak of the renormalized chiral
susceptibility predicts =151(3)(3) MeV, wheres -s based on the
strange quark number susceptibility and Polyakov loops result in 24(4) MeV and
25(4) MeV larger values, respectively. Another consequence of the cross-over is
the non-vanishing width of the peaks even in the thermodynamic limit, which we
also determine. These numbers are attempted to be the full result for the
0 transition, though other lattice fermion formulations (e.g. Wilson)
are needed to cross-check them.Comment: 13 pages 5 figures. Final version, published in Phys.Lett.
The equation of state in lattice QCD: with physical quark masses towards the continuum limit
The equation of state of QCD at vanishing chemical potential as a function of
temperature is determined for two sets of lattice spacings. Coarser lattices
with temporal extension of N_t=4 and finer lattices of N_t=6 are used. Symanzik
improved gauge and stout-link improved staggered fermionic actions are applied.
The results are given for physical quark masses both for the light quarks and
for the strange quark. Pressure, energy density, entropy density, quark number
susceptibilities and the speed of sound are presented.Comment: 14 pages, 9 figures. Version published in JHEP: discussions added in
Sects. 1, 2. Fig. 1 changed and a new figure for the interaction measure
added. Information on statistics added in Table 1. Raw values of the pressure
added in Table 3. A few references adde
Variations in Arterial Blood Pressure after Kidney Transplantation
The course of hypertension within the first 2 months after kidney transplantation was correlated with renal function, plasma renin activity (PRA), and the daily maintenance dose of prednisone in 18 homograft recipients. During acute rejection blood pressure (BP) closely correlated with PRA. Patients with normal homograft function showed an increase in BP early after transplantation which in most returned to normal 3-8 weeks later. In the latter group no correlation could be found between the level of BP and PRA, however the BP correlated closely with the dose of prednisone. These observations suggest that during acute rejection the increase in BP may at least partly be mediated by a renal pressor mechanism, whereas with normal renal function the high dose of glucocorticoids may play an important role in the development of hypertension.</jats:p
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