Nuclear Theory·nucl-th

Tuesday·April 3, 2018

12 papers—7 primary·5 cross-listed

08
Non-hydrodynamic quasinormal modes and equilibration of a baryon dense holographic QGP with a critical point
Romulo Rougemont (IIP, Brazil)🇧🇷 · Renato Critelli (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U.)🇧🇷
We compute the homogeneous limit of non-hydrodynamic quasinormal modes (QNM's) of a phenomenologically realistic Einstein-Maxwell-Dilaton (EMD) holographic model for the Quark-Gluon Plasma (QGP) that is able to: i) {\it quantitatively} describe state-of-the-art lattice results for the QCD equation of state and higher order baryon susceptibilities with $2 + 1$ flavors and physical quark masses up to highest values of the baryon chemical potential currently reached in lattice simulations; ii) describe the nearly perfect fluidity of the strongly coupled QGP produced in ultrarelativistic heavy ion collisions; iii) give a very good description of the bulk viscosity extracted via some recent Bayesian analyzes of hydrodynamical descriptions of heavy ion experimental data. This EMD model has been recently used to predict the location of the QCD critical point in the QCD phase diagram, which was found to be within the reach of upcoming low energy heavy ion collisions. The lowest quasinormal modes of the $S O (3)$ rotationally invariant quintuplet, triplet, and singlet channels evaluated in the present work provide upper bounds for characteristic equilibration times describing how fast the dense medium returns to thermal equilibrium after being subjected to small disturbances. We find that the equilibration times in the different channels come closer to each other at high temperatures, although being well separated at the critical point. Moreover, in most cases, these equilibration times decrease with increasing baryon chemical potential while keeping temperature fixed.
↳ hep-phhep-thnucl-thPRD(2018)·26 citations
09
Cooling of Small and Massive Hyperonic Stars
Rodrigo Negreiros🇧🇷 · Laura Tolos🇩🇪 · Mario Centelles🇪🇸 · Angels Ramos🇪🇸 · Veronica Dexheimer🇺🇸
We perform cooling simulations for isolated neutron stars using recently developed equations of state for their core. The equations of state are obtained from new parametrizations of the FSU2 relativistic mean-field functional that reproduce the properties of nuclear matter and finite nuclei, while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions, measurements of massive 2 $M_{⊙}$ neutron stars, and neutron star radii below 13 km. We find that two of the models studied, FSU2R (with nucleons) and in particular FSU2H (with nucleons and hyperons), show very good agreement with cooling observations, even without including extensive nucleon pairing. This suggests that the cooling observations are more compatible with an equation of state that produces a soft nuclear symmetry energy and, hence, generates small neutron star radii. However, both models favor large stellar masses, above $1.8 M_{⊙}$ , to explain the colder isolated neutron stars that have been observed, even if nucleon pairing is present.
↳ astro-ph.HEnucl-thApJ(2018)·65 citations
10
Pulsars as Weber gravitational wave detectors
Arpan Das🇮🇳 · Shreyansh S. Dave🇮🇳 · Oindrila Ganguly🇮🇳 · Ajit M. Srivastava🇮🇳
A gravitational wave passing through a pulsar will lead to a variation in the moment of inertia of the pulsar affecting its rotation. This will affect the extremely accurately measured spin rate of the pulsar as well as its pulse profile (due to induced wobbling depending on the source direction). The effect will be most pronounced at resonance and should be detectable by accurate observations of the pulsar signal. The pulsar, in this sense, acts as a remotely stationed Weber detector of gravitational waves whose signal can be monitored on earth. With possible gravitational wave sources spread around in the universe, pulsars in their neighborhoods can provide us a family of \textit{remote} detectors all of which can be monitored on earth. Even if GW are detected directly by earth based conventional detectors, such pulsar detectors can provide additional information for accurate determination of the source location. This can be of crucial importance for sources which do not emit any other form of radiation such as black hole mergers. For the gravitational wave events already detected by LIGO (and Virgo), our proposal suggests that one should look for specific pulsars which would have been disturbed by these events, and will transmit this disturbance via their pulse signals in any foreseeable future. If these future pulsar events can be predicted with accuracy then a focused effort can be made to detect any possible changes in the signals of those specific pulsars.
↳ astro-ph.HEgr-qcnucl-thPLB(2019)·8 citations
11
$^{9}$ Be+ $^{120}$ Sn scattering at near-barrier energies within a four body model
A. Arazi · J. Casal · M. Rodríguez-Gallardo · J. M. Arias · R. Lichtenthäler Filho · D. Abriola · O. A. Capurro · M. A. Cardona · P. F. F. Carnelli · E. de Barbará · J. Fernández Niello · J. M. Figueira and 5 other authors
Cross sections for elastic and inelastic scattering of the weakly-bound $^{9}$ Be nucleus on a $^{120}$ Sn target have been measured at seven bombarding energies around and above the Coulomb barrier. The elastic angular distributions are analyzed with a four-body continuum-discretized coupled-channels (CDCC) calculation, which considers $^{9}$ Be as a three-body projectile ( $α$ + $α$ + n). An optical model analysis using the São Paulo potential is also shown for comparison. The CDCC analysis shows that the coupling to the continuum part of the spectrum is important for the agreement with experimental data even at energies around the Coulomb barrier, suggesting that breakup is an important process at low energies. At the highest incident energies, two inelastic peaks are observed at 1.19(5) and 2.41(5) MeV. Coupled-channels (CC) calculations using a rotational model confirm that the first inelastic peak corresponds to the excitation of the 2 $_{1}^{+}$ state in $^{120}$ Sn, while the second one likely corresponds to the excitation of the 3 $_{1}^{-}$ state.
↳ nucl-exnucl-thPRC(2018)·30 citations
12
Probing confinement by direct photons and dileptons
V.V. Goloviznin🇺🇦 · A.V. Nikolskii🇷🇺 · A.M. Snigirev🇷🇺 · G.M. Zinovjev🇺🇦
The intensive synchrotron radiation resulting from quarks interacting with the collective confining color field in relativistic heavy ion collisions is discussed. The spectrum of photons with large transverse momentum is calculated and compared with the experimental data to demonstrate the feasibility of this type of radiation. A study of the earlier predicted azimuthal anisotropy in the angular distribution of dileptons with respect to the three-momentum of the pair is performed as well. This boundary-induced mechanism of lepton pair production is shown to possess the features that are distinctly different from the standard mechanisms and can potentially provide an efficient probe of quark-gluon plasma formation.
↳ hep-phnucl-exnucl-thEPJA(2019)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Non-hydrodynamic quasinormal modes and equilibration of a baryon dense holographic QGP with a critical point

Cooling of Small and Massive Hyperonic Stars

Pulsars as Weber gravitational wave detectors

9Be+120Sn scattering at near-barrier energies within a four body model

Probing confinement by direct photons and dileptons

Affiliations

$^{9}$ Be+ $^{120}$ Sn scattering at near-barrier energies within a four body model