2,277 research outputs found
Thermalization through Hagedorn states - the importance of multiparticle collisions
Quick chemical equilibration times of hadrons within a hadron gas are
explained dynamically using Hagedorn states, which drive particles into
equilibrium close to the critical temperature. Within this scheme master
equations are employed for the chemical equilibration of various hadronic
particles like (strange) baryon and antibaryons. A comparison of the Hagedorn
model to recent lattice results is made and it is found that for both Tc =176
MeV and Tc=196 MeV, the hadrons can reach chemical equilibrium almost
immediately, well before the chemical freeze-out temperatures found in thermal
fits for a hadron gas without Hagedorn states.Comment: 8 pages, 3 figures, talk presented at the International Conference on
Strangeness in Quark Matter, Buzios, Rio de Janeiro, Brazil, Sept. 27 - Oct.
2, 200
Particle Ratios as a Probe of the QCD Critical Temperature
We show how the measured particle ratios can be used to provide non-trivial
information about the critical temperature of the QCD phase transition. This is
obtained by including the effects of highly massive Hagedorn resonances on
statistical models, which are used to describe hadronic yields. The inclusion
of Hagedorn states creates a dependence of the thermal fits on the Hagedorn
temperature, , which is assumed to be equal to , and leads to an
overall improvement of thermal fits. We find that for Au+Au collisions at RHIC
at GeV the best square fit measure, , occurs at
MeV and produces a chemical freeze-out temperature of 172.6 MeV
and a baryon chemical potential of 39.7 MeV.Comment: 6 pages, 4 figure
Particle Ratios and the QCD Critical Temperature
We show how the measured particle ratios at RHIC can be used to provide
non-trivial information about the critical temperature of the QCD phase
transition. This is obtained by including the effects of highly massive
Hagedorn resonances on statistical models, which are used to describe hadronic
yields. Hagedorn states are relevant close to and have been shown to
decrease to the KSS limit and allow for quick chemical equilibrium
times in dynamical calculations of hadrons. The inclusion of Hagedorn states
creates a dependence of the thermal fits on the Hagedorn temperature, ,
which is assumed to be equal to , and leads to an overall improvement of
thermal fits. We find that for Au+Au collisions at RHIC at
GeV the best square fit measure, , occurs at MeV and
produces a chemical freeze-out temperature of 170.4 MeV and a baryon chemical
potential of 27.8 MeV.Comment: 6 pages, 2 figures, talk presented at the International Conference on
Strangeness in Quark Matter, Buzios, Rio de Janeiro, Brazil, Sept. 27 - oct.
2, 200
Fast Equilibration of Hadrons in an Expanding Fireball
Due to long chemical equilibration times within standard hadronic reactions
during the hadron gas phase in relativistic heavy ion collisions it has been
suggested that the hadrons are "born" into equilibrium after the quark gluon
plasma phase. Here we develop a dynamical scheme in which possible Hagedorn
states contribute to fast chemical equilibration times of baryon anti-baryon
pairs (as well as kaon anti-kaon pairs) inside a hadron gas and just below the
critical temperature. Within this scheme, we use master equations and derive
various analytical estimates for the chemical equilibration times. Applying a
Bjorken picture to the expanding fireball, the kaons and baryons as well as the
bath of pions and Hagedorn resonances can indeed quickly chemically equilibrate
for both an initial overpopulation or underpopulation of Hagedorn resonances.
Moreover, a comparison of our results to and
ratios at RHIC, indeed, shows a close match.Comment: 4 pages, 5 figure
Vanishing DC holographic conductivity from a magnetic monopole condensate
We show how to obtain a vanishing DC conductivity in 3-dimensional strongly
coupled QFT's using a massive 2-form field in the bulk that satisfies a special
kind of boundary condition. The real and imaginary parts of the AC conductivity
are evaluated in this holographic setup and we show that the DC conductivity
identically vanishes even for an arbitrarily small (though nonzero) value of
the 2-form mass in the bulk. We identify the bulk action of the massive 2-form
with an effective theory describing a phase in which magnetic monopoles have
condensed in the bulk. Our results indicate that a condensate of magnetic
monopoles in a 4-dimensional bulk leads to a vanishing DC holographic
conductivity in 3-dimensional strongly coupled QFT's.Comment: 24 pages, 2 figures, accepted for publication in JHE
Hardware-Accelerated Machine Vision using Field-Programmable Gate Arrays (FPGA)
A hardware-accelerated vision system for object tracking was developed and implemented using FPGAs. Based on Amdahl’s Law equation, the final hardware design outperformed a similar software implementation by a factor of 7.7
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