Transverse momentum dependence of transverse flow in relativistic heavy-ion collisions

The strength of transverse flow is examined as a function of transverse momentum $p_t$ using a simple, transversely moving thermal model and a more realistic, relativistic transport model (ART). It is shown that the $p_t$ dependence reveals useful information about the collective flow that is complementary to that obtained from the standard in-plane transverse momentum analysis. Interesting features of using the $p_t$ dependence to study the equation of state of the superdense hadronic matter formed in relativistic heavy-ion collisions are demonstrated.Comment: Latex file, 10 pages, 3 figures availabe upon request; Phys. Rev. C (Aug., 1996) in pres

Rapidity distribution as a probe for elliptical flow at intermediate energies

Interplay between the spectator and participant matter in heavy-ion collisions is investigated within isospin dependent quantum molecular dynamics (IQMD) model in term of rapidity distribution of light charged particles. The effect of different types and size rapidity distributions is studied in elliptical flow. The elliptical flow patterns show important role of the nearby spectator matter on the participant zone. This role is further explained on the basis of passing time of the spectator and expansion time of the participant zone. The transition from the in-plane to out-of-plane is observed only when the mid-rapidity region is included in the rapidity bin, otherwise no transition occurs. The transition energy is found to be highly sensitive towards the size of the rapidity bin, while weakly on the type of the rapidity distribution. The theoretical results are also compared with the experimental findings and are found in good agreement.Comment: 8 figure

On Physical Equivalence between Nonlinear Gravity Theories

We argue that in a nonlinear gravity theory, which according to well-known results is dynamically equivalent to a self-gravitating scalar field in General Relativity, the true physical variables are exactly those which describe the equivalent general-relativistic model (these variables are known as Einstein frame). Whenever such variables cannot be defined, there are strong indications that the original theory is unphysical. We explicitly show how to map, in the presence of matter, the Jordan frame to the Einstein one and backwards. We study energetics for asymptotically flat solutions. This is based on the second-order dynamics obtained, without changing the metric, by the use of a Helmholtz Lagrangian. We prove for a large class of these Lagrangians that the ADM energy is positive for solutions close to flat space. The proof of this Positive Energy Theorem relies on the existence of the Einstein frame, since in the (Helmholtz--)Jordan frame the Dominant Energy Condition does not hold and the field variables are unrelated to the total energy of the system.Comment: 37 pp., TO-JLL-P 3/93 Dec 199

Unruh--DeWitt detectors in spherically symmetric dynamical space-times

In the present paper, Unruh--DeWitt detectors are used in order to investigate the issue of temperature associated with a spherically symmetric dynamical space-times. Firstly, we review the semi-classical tunneling method, then we introduce the Unruh--DeWitt detector approach. We show that for the generic static black hole case and the FRW de Sitter case, making use of peculiar Kodama trajectories, semiclassical and quantum field theoretic techniques give the same standard and well known thermal interpretation, with an associated temperature, corrected by appropriate Tolman factors. For a FRW space-time interpolating de Sitter space with the Einstein--de Sitter universe (that is a more realistic situation in the frame of $\Lambda$CDM cosmologies), we show that the detector response splits into a de Sitter contribution plus a fluctuating term containing no trace of Boltzmann-like factors, but rather describing the way thermal equilibrium is reached in the late time limit. As a consequence, and unlike the case of black holes, the identification of the dynamical surface gravity of a cosmological trapping horizon as an effective temperature parameter seems lost, at least for our co-moving simplified detectors. The possibility remains that a detector performing a proper motion along a Kodama trajectory may register something more, in which case the horizon surface gravity would be associated more likely to vacuum correlations than to particle creation.Comment: 19 pages, to appear on IJTP. arXiv admin note: substantial text overlap with arXiv:1101.525

Body temperature of the Atlantic bluefin tuna (Thunnun thynnus L.) in the Western Mediterranean

This study documents body temperature in the Atlantic bluefin tuna (Thunnus thynnus L.) in the Mediterranean Sea and temperature variability caused by the stress of capture. The investigation was carried out in the traditional trap (tonnara) of Isola Piana (Sardinia, W Mediterranean) where body temperature recordings were conducted on free-swimming bluefin confined in the system of nets known as “camere” or chambers. We tracked the body temperature of two bluefin tuna (214 and 191 cm CFL) using a commercial data logger (HOBO U12, Onset Computer Corporation), under two conditions: the pre-fishing phase, when specimens confined in the “camera di ponente” are undisturbed and the fishing phase when bluefin tuna are trapped in the “camera della morte” and undergo the stress of confinement and capture (mattanza). Body temperature increased by about 2°C during the “mattanza”, whereas no temperature variation was exhibited during the pre-fishing phase. The heat transfer coefficient (K), calculated for both bluefin tuna during the “mattanza”, revealed a rapid increase in heat transfer. Additional data on ambient temperature Ta, white muscle Tw (n = 65; 110–287 cm CFL) and red muscle temperature Tr, (n = 249; 107–287 cm CFL) were obtained from live fish during angling operations, and excess body temperature (Tx = Tr–Ta) was calculated. Mean red muscle temperature was 27.6 ± 1.48°C in an ambient temperature of 18.9 ± 0.84°C. The excess red muscle temperature Tx was 8.21–9.10°C, and the red muscle was 2.4 ± 1.78°C warmer than white muscle