Nuclear Theory·nucl-th

Friday·May 29, 2015

9 papers—5 primary·4 cross-listed

06
[Submitted on 28 May 2015] (cross-list from astro-ph.HE)
Angular Momentum Role in the Hypercritical Accretion of Binary-Driven Hypernovae
L. Becerra · F. Cipolletta · C. L. Fryer · Jorge A. Rueda · R. Ruffini
The induced gravitational collapse (IGC) paradigm explains a class of energetic, $E_{iso} ≳ 1 0^{52}$ ~erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae (BdHNe). The progenitor is a tight binary system formed of a carbon-oxygen (CO) core and a neutron star companion. The supernova ejecta of the exploding CO core triggers a hypercritical accretion process onto the neutron star, which reaches in a few seconds the critical mass, and gravitationally collapses to a black hole emitting a GRB. In our previous simulations of this process we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, $L_{acc}$ , and perform numerical simulations of the angular momentum transfer to the neutron star during the hyperaccretion process in full general relativity. We show that the neutron star: i) reaches in a few seconds either mass-shedding limit or the secular axisymmetric instability depending on its initial mass; ii) reaches a maximum dimensionless angular momentum value, $[c J / (G M^{2})]_{max} \approx 0.7$ ; iii) can support less angular momentum than the one transported by supernova ejecta, $L_{acc} > J_{NS, max}$ , hence there is an angular momentum excess which necessarily leads to jetted emission.
Comments:
Accepted for publication in Astrophysical Journal
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1505.07580 [pdf]
ApJ(2015)·60 citations
07
[Submitted on 28 May 2015] (cross-list from hep-ph)
QCD Equation of State and Cosmological Parameters in Early Universe
Paolo Castorina🇮🇹 · Vincenzo Greco🇮🇹 · Salvatore Plumari🇮🇹
The time evolution of cosmological parameters in early Universe at the deconfinement transition is studied by an equation of state (EoS) which takes into account the finite baryon density and the background magnetic field. The non perturbative dynamics is described by the Field Correlator Method (FCM) which gives, with a small number of free parameters, a good fit of lattice data. The entire system has two components, i.e. the quark-gluon plasma and the electroweak sector, and the solutions of the Friedmann equation show that the scale factor, $a (t)$ , and $H (t) = (1/ a) d a / d t$ are weakly dependent on the EoS, but the deceleration parameter, $q (t)$ , and the jerk, $j (t)$ , are strongly modified above the critical temperature $T_{c}$ , corresponding to a critical time $t_{c} ≃ 20 - 25 μ s$ . The time evolution of the cosmological parameters suggest that above and around $T_{c}$ there is a transient state of acceleration typical of a matter dominated Universe; this is entailed by the QCD strong interaction driven by the presence of massive colored objects.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
arXiv:
1505.07655 [pdf]
PRD(2015)·13 citations
08
[Submitted on 28 May 2015] (cross-list from gr-qc)
Quantum corrections to the stress-energy tensor in thermodynamic equilibrium with acceleration
F. Becattini🇮🇹 · E. Grossi (University of Florence, Italy)🇮🇹
We show that the stress-energy tensor has additional terms with respect to the ideal form in states of global thermodynamic equilibrium in flat spacetime with non-vanishing acceleration and vorticity. These corrections are of quantum origin and their leading terms are second order in the gradients of the thermodynamic fields. Their relevant coefficients can be expressed in terms of correlators of the stress-energy tensor operator and the generators of the Lorentz group. With respect to previous assessments, we find that there are more second order coefficients and that all thermodynamic functions including energy density receive acceleration and vorticity dependent corrections. Notably, also the relation between \rho and p, that is the equation of state, is affected by acceleration and vorticity. We have calculated the corrections for a free real scalar field -- both massive and massless -- and we have found that they increase, particularly for a massive field, at very high acceleration and vorticity and very low temperature. Finally, these non-ideal terms depend on the explicit form of the stress-energy operator, implying that different stress-energy tensor of the scalar field -- canonical or improved -- are thermodynamically inequivalent.
Comments:
18 pages, 1 figure. Minor changes, to appear in PRD
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1505.07760 [pdf]
PRD(2015)·77 citations
09
[Submitted on 28 May 2015] (cross-list from nucl-ex)
Azimuthal anisotropy in U+U and Au+Au collisions at RHIC
STAR Collaboration: L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · J. Alford · A. Aparin · D. Arkhipkin · E. C. Aschenauer · G. S. Averichev · V. Bairathi and 320 other authors
Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, $v_{2} {2}$ and $v_{2} {4}$ , for charged hadrons from U+U collisions at $s_{NN}$ = 193 GeV and Au+Au collisions at $s_{NN}$ = 200 GeV. Nearly fully overlapping collisions are selected based on the amount of energy deposited by spectators in the STAR Zero Degree Calorimeters (ZDCs). Within this sample, the observed dependence of $v_{2} {2}$ on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. An initial-state model with gluon saturation describes the slope of $v_{2} {2}$ as a function of multiplicity in central collisions better than one based on Glauber with a two-component multiplicity model.
Comments:
Final paper version accepted for publication in Phys. Rev. Lett. New version includes comparisons to a constituent quark glauber model
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1505.07812 [pdf]
PRL(2015)·169 citations

Affiliations

first authorsco-authorsvia INSPIRE

Angular Momentum Role in the Hypercritical Accretion of Binary-Driven Hypernovae

QCD Equation of State and Cosmological Parameters in Early Universe

Quantum corrections to the stress-energy tensor in thermodynamic equilibrium with acceleration

Azimuthal anisotropy in U+U and Au+Au collisions at RHIC

Affiliations