2,250 research outputs found
Viscosity near phase transitions
Probably the most enticing observation in theoretical physics during the last
decade was the discovery of the great amount of consequences obtained from the
AdS/CFT conjecture put forward by Maldacena. In this work we review how this
correspondence can be used to address hydrodynamic properties such as the
viscosity of some strongly interacting systems. We also employ the Boltzmann
equation for those systems closer to low-energy QCD, and argue that this kind
of transport coefficients can be related to phase transitions, in particular
the QGP/hadronic phase transition studied in heavy ion collisions.Comment: 9 pages, 1 figure. Contribution to the Gribov-80 Memorial Workshop.
ICTP Trieste, Italy, May 26-28, 201
FOOD SAFETY SHOCKS AND THEIR EFFECT ON INTERNATIONAL COMPETITIVENESS: A CASE STUDY FROM THE GUATEMALAN RASPBERRY INDUSTRY
This document contains the PowerPoint presentation given by the authors at the 2002 WCC-72 meetings, regarding food safety shocks and their effect on international competitiveness.Food Consumption/Nutrition/Food Safety, International Relations/Trade,
D-meson diffusion in hadronic matter
We present effective-field-theory results with unitarized interactions on the
D-meson transport coefficients in a gas populated by light mesons and baryons
at finite temperature and baryochemical potential. The Fokker-Planck equation
is used to compute the drag force, the relaxation time and the diffusion
coefficients of D mesons for collisions at FAIR. At finite baryochemical
potential, the combined effect of net baryonic density and sizable meson-baryon
interaction makes the D mesons to relax more efficiently than in the case at
zero baryochemical potential. We also describe the connection with the
quark-gluon plasma phase in adiabatic trajectories on the phase diagram at both
zero and finite baryochemical potential.Comment: 5 pages, 4 figures. Contribution to the FAIRNESS 2013 - Workshop for
young scientists with research interests focused on FAIR physics. 15-21
September 2013, Berlin (Germany
Heavy Quark Fluorescence
Heavy hadrons containing heavy quarks (for example, Upsilon-mesons) feature a
scale separation between the heavy quark mass (about 4.5 GeV for the b-quark)
and the QCD scale (about 0.3 GeV}) that controls effective masses of lighter
constituents. Therefore, as in ordinary molecules, the de-excitation of the
lighter, faster degrees of freedom leaves the velocity distribution of the
heavy quarks unchanged, populating the available decay channels in
qualitatively predictable ways. Automatically an application of the
Franck-Condon principle of molecular physics explains several puzzling results
of Upsilon(5S) decays as measured by the Belle collaboration, such as the high
rate of Bs*-anti Bs* versus Bs*-anti Bs production, the strength of three-body
B-anti B + pion decays, or the dip in B momentum shown in these decays. We
argue that the data is showing the first Sturm-Liouville zero of the
Upsilon(5S) quantum mechanical squared wavefunction, and providing evidence for
a largely b-anti b composition of this meson.Comment: 4 pages, 4 figures, Figure 2 updated and some typos corrected. To be
published in Physical Review Letter
Minimum of and the phase transition of the Linear Sigma Model in the large-N limit
We reexamine the possibility of employing the viscosity over entropy density
ratio as a diagnostic tool to identify a phase transition in hadron physics to
the strongly coupled quark-gluon plasma and other circumstances where direct
measurement of the order parameter or the free energy may be difficult.
It has been conjectured that the minimum of eta/s does indeed occur at the
phase transition. We now make a careful assessment in a controled theoretical
framework, the Linear Sigma Model at large-N, and indeed find that the minimum
of eta/s occurs near the second order phase transition of the model due to the
rapid variation of the order parameter (here the sigma vacuum expectation
value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added,
typos corrected and certain arguments clarified, revised for PR
Thermal Risk Mitigation Testing of the DarkNESS Observatory for Fermi NationalAccelerator Laboratory
This paper presents the prototype design and laboratory test results of the thermal control system for the Dark matter as sterile Neutrino Search Satellite (DarkNESS). A collaboration between Fermilab, CU Aerospace, and the University of Illinois Department of Aerospace Engineering’s Laboratory for Advanced Space Systems (LASSI), the 6U satellite uses a Skipper CCD to detect weak 3.55 – 3.57 keV X-ray emissions, previously discovered by the XMM-Newton and Chandra X-ray observatories. To minimize read-out noise, the thermal control system incorporates a 10 W integral rotary cryocooler and passive heat transfer elements, maintaining the CCD at an operating temperature of 170 K. Analyses of the Earth\u27s obstruction of the instrument’s field of view and the impact of external heating on the instrument aperture established performance requirements and attitude constraints for the thermal control system. A high-fidelity test of a preliminary design was performed in a thermal vacuum chamber, prompting modifications to improve the thermal system design margins. This effort precedes the Critical Design Review milestone
and Phase Transitions
We present a calculation of eta/s for the meson gas (zero baryon number),
with the viscosity computed within unitarized NLO chiral perturbation theory,
and confirm the observation that eta/s decreases towards the possible phase
transition to a quark-gluon plasma/liquid. The value is somewhat higher than
previously estimated in LO chi PT. We also examine the case of atomic Argon gas
to check the discontinuity of eta/s across a first order phase transition. Our
results suggest employing this dimensionless number, sometimes called KSS
number (in analogy with other ratios in fluid mechanics such as Reynolds number
or Prandtl number) to pin down the phase transition and critical end point to a
cross-over in strongly interacting nuclear matter between the hadron gas and
quark and gluon plasma/liquid.Comment: Revised for PRD. Shorter (by one section) than first version. 6 pp, 4
figure
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