121 research outputs found
Hadronic correlations above the chiral/deconfinement transition
The statistical bootstrap model is critically revised in order to include a
medium-dependent resonance width in it. We show that a thermodynamic model with
a vanishing width below the Hagedorn temperature T_H and a Hagedorn
spectrum-like width above T_H may not only eliminate the divergence of the
thermodynamic functions above T_H, but also gives a satisfactory description
the lattice quantum chromodynamics (QCD) data on the energy density above the
chiral/deconfinement transition as the main result of this contribution. This
model allows to explain the absence of heavy resonance contributions in the fit
of the experimentally measured particle ratios at SPS and RHIC energies.Comment: 9 pages, 2 figures, contribution to proceedings of NAPP 2003,
Dubrovnik, Croatia, 26-31 May, 200
Mott effect at the chiral phase transition and anomalous J/Psi suppression
We investigate the in-medium modification of the charmonium break-up
processes due to the Mott effect for light (pi) and open-charm (D, D*) mesons
at the chiral/deconfinement phase transition. A model calculation for the
process J/Psi + pi -> D + \bar D* + h.c. is presented which demonstrates that
the Mott effect for the D-mesons leads to a threshold effect in the thermal
averaged break-up cross section. This effect is suggested as an explanation of
the phenomenon of anomalous J/Psi suppression in the CERN NA50 experiment.Comment: 9 pages, 3 figures; final version to appear in Phys. Lett.
Implications from GW170817 and I-Love-Q relations for relativistic hybrid stars
Gravitational wave observations of GW170817 placed bounds on the tidal
deformabilities of compact stars allowing one to probe equations of state for
matter at supranuclear densities. Here we design new parametrizations for
hybrid hadron-quark equations of state, that give rise to low-mass twin stars,
and test them against GW170817. We find that GW170817 is consistent with the
coalescence of a binary hybrid star--neutron star. We also test and find that
the I-Love-Q relations for hybrid stars in the third family agree with those
for purely hadronic and quark stars within for both slowly and
rapidly rotating configurations, implying that these relations can be used to
perform equation-of-state independent tests of general relativity and to break
degeneracies in gravitational waveforms for hybrid stars in the third family as
well.Comment: 8 pages, 4 figures, 2 tables; matches published version, updated fig.
Conformal relativity versus Brans-Dicke and superstring theories
Conformal relativity theory which is also known as Hoyle-Narlikar theory has
recently been given some new interest. It is an extended relativity theory
which is invariant with respect to conformal transformations of the metric.
In this paper we show how conformal relativity is related to the Brans-Dicke
theory and to the low-energy-effective superstring theory. We show that
conformal relativity action is equaivalent to a transformed Brans-Dicke action
for Brans-Dicke parameter in contrast to a reduced
(graviton-dilaton) low-energy-effective superstring action which corresponds to
a Brans-Dicke action with Brans-Dicke parameter . In fact,
Brans-Dicke parameter gives a border between a standard scalar
field evolution and a ghost.
We also present basic cosmological solutions of conformal relativity in both
Einstein and string frames. The Eintein limit for flat conformal cosmology
solutions is unique and it is flat Minkowski space. This requires the scalar
field/mass evolution instead of the scale factor evolution in order to explain
cosmological redshift.
It is interesting that like in ekpyrotic/cyclic models, a possible transition
through a singularity in conformal cosmology in the string frame takes place in
the weak coupling regime.Comment: REVTEX4, 12 pages, an improved version, references adde
Hadronske korelacije iznad prijelaza kiralnost – odsužnjivanje
The statistical bootstrap model is critically revised in order to include a medium-dependent resonance width in it. We show that a thermodynamic model with a vanishing width below the Hagedorn temperature TH and a Hagedorn spectrum-like width above TH may not only eliminate the divergence of the thermodynamic functions above TH, but also gives a satisfactory description of the lattice quantum chromodynamics data on the energy density above the chiral/deconfinement transition as the main result of this contribution. This model allows us to explain the absence of heavy resonance contributions in the fit of the experimentally measured particle ratios at SPS and RHIC energies.Kritički prerađujemo statistički model samopodizanja kako bi u njega uključili širine rezonancija ovisne o sredini. Pokazujemo da termodinamički model s iščezavajućom širinom ispod Hagedornove temperature TH, i sa spektralnom širinom poput Hagedornovove iznad TH, može ukloniti divergenciju termodinamičkih funkcija iznad TH, ali on također daje dobar opis podataka kvantne kromodinamike na rešetci za gustoću energije iznad prijelaza kiralnost – odsužnjivanje, što je glavni doprinos ovog rada. Taj model objašnjava nepojavljivanje teških rezonancija u mjerenjima eksperimentalnih čestičnih omjera na energijama SPS i RHIC
Observable effects caused by vacuum pair creation in the field of high-power optical lasers
We consider the possibility of an experimental proof of vacuum e+e- pair
creation in the focus of two counter-propagating optical laser beams with an
intensity of the order of 10^20 - 10^22 W/cm^2. Our approach is based on the
collisionless kinetic equation for the distribution function of the e+e- pairs
with the source term for particle production. As a possible experimental signal
of vacuum pair production we consider the refraction of a high-frequency probe
laser beam by the produced e+e- plasma to be observed by an interference
filter. The generation of higher harmonics of the laser frequency in the
self-consistent electric field is also investigated.Comment: 7 pages, 7 figures; typos corrected, Eq.(16) corrected, reference
adde
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