neven bilic - Academia.edu (original) (raw)
Papers by neven bilic
Progress in Particle and Nuclear Physics, 2002
After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the st... more After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the star S0–1, which has the smallest projected distance to Sgr A∗, in the supermassive black hole as well as in the fermion ball scenarios of the Galactic center. It is shown that both scenarios are consistent with the data, as measured during the last six years by Genzel et al. and Ghez et al. We then consider a self-gravitating ideal fermion gas at nonzero temperature as a model for the Galactic halo. The Galactic halo of mass ∼ 2 × 1012M⊙ enclosed within a radius of ∼ 200 kpc implies the existence of a supermassive compact dark object at the Galactic center that is in hydrostatic and thermal equilibrium with the halo. The central object has a maximal mass of ∼ 2.3 × 106M⊙ within a minimal radius of ∼ 18 mpc or ∼ 21 light-days for fermion masses ∼ 15 keV. We thus conclude that both the supermassive compact dark object and the halo could be made of the same weakly interacting ∼ 15 keV particle.
Phys Rev D, 1982
We study the production of two gluons and one photon in e+e- collisions, in particular the proces... more We study the production of two gluons and one photon in e+e- collisions, in particular the process in which the intermediate resonance is the neutral weak vector boson Z0. We compare the cross section of this process with the cross section of the lower-order process in which two quarks and one photon are produced. We find that ggγ production is unimportant in comparison with q¯qγ production except near phase-space boundaries on the Z0 resonance.
Physical Review D, Jul 1, 1980
We investigate the quark gas at finite temperatures and densities including nonperturbative effec... more We investigate the quark gas at finite temperatures and densities including nonperturbative effects in the framework of quantum chromodynamics. In our calculations we use the dilute-gas approximation for the thermodynamics of the finite-temperature instanton gas. For the suppression of large-scale instantons we consider the color-charge screening. The nonperturbative results can be compared directly from our numerical evaluations with those of the perturbation calculations.
Ijmpa, 1995
We review the relationship between the pion decay constant fπ, the chiral symmetry restoration te... more We review the relationship between the pion decay constant fπ, the chiral symmetry restoration temperature Tc and the phenomenology of low energy chiral symmetry breaking in view of the recent confirmation of the existence of a sigma meson with a mass of 600-700 MeV.
We investigate the correspondence between a perfect fluid and a scalar field and show a possible ... more We investigate the correspondence between a perfect fluid and a scalar field and show a possible way of expressing thermodynamic quantities such as entropy, particle number density, temperature and chemical potential in terms of the scalar field phi and its kinetic term X. We prove a theorem which relates isentropy with purely kinetic Lagrangian. As an application, we study the evolution of the gravitational potential in cosmological perturbation theory.
Nuclear Physics B, Oct 1, 1981
We investigate the instanton paramagnetic medium at finite temperature. By analyzing the equation... more We investigate the instanton paramagnetic medium at finite temperature. By analyzing the equation of state we show explicitly the presence of both first- and second- order phase transitions. Within the known framework of the mean field type of approximations we also include the effects of large-scale vacuum fluctuations. The numerical results are compared to other approaches to this problem in quantum chromodynamics at finite temperature.
Physics Letters B, Nov 5, 1979
We investigate the nonperturbative effects in QCD at finite density and temperature. Within the d... more We investigate the nonperturbative effects in QCD at finite density and temperature. Within the dilute gas approximation we estimate explicitly these effects at high densities. These results are compared with perturbation calculations.
Physical Review D Particles and Fields, Jul 1, 2009
We consider the prospects for dark matter/energy unification in k-essence type cosmologies. Gener... more We consider the prospects for dark matter/energy unification in k-essence type cosmologies. General mappings are established between the k-essence scalar field, the hydrodynamic and braneworld descriptions. We develop an extension of the general relativistic dust model that incorporates the effects of both pressure and the associated acoustic horizon. Applying this to a tachyon model, we show that this inhomogeneous “variable Chaplygin gas” does evolve into a mixed system containing cold dark matter like gravitational condensate in significant quantities. Our methods can be applied to any dark energy model, as well as to mixtures of dark energy and traditional dark matter.
Physical review D: Particles and fields
ABSTRACT
Physical Review D
ABSTRACT
Physical Review D
ABSTRACT
Progress in Particle and Nuclear Physics, 2002
After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the st... more After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the star S0–1, which has the smallest projected distance to Sgr A∗, in the supermassive black hole as well as in the fermion ball scenarios of the Galactic center. It is shown that both scenarios are consistent with the data, as measured during the last six years by Genzel et al. and Ghez et al. We then consider a self-gravitating ideal fermion gas at nonzero temperature as a model for the Galactic halo. The Galactic halo of mass ∼ 2 × 1012M⊙ enclosed within a radius of ∼ 200 kpc implies the existence of a supermassive compact dark object at the Galactic center that is in hydrostatic and thermal equilibrium with the halo. The central object has a maximal mass of ∼ 2.3 × 106M⊙ within a minimal radius of ∼ 18 mpc or ∼ 21 light-days for fermion masses ∼ 15 keV. We thus conclude that both the supermassive compact dark object and the halo could be made of the same weakly interacting ∼ 15 keV particle.
Phys Rev D, 1982
We study the production of two gluons and one photon in e+e- collisions, in particular the proces... more We study the production of two gluons and one photon in e+e- collisions, in particular the process in which the intermediate resonance is the neutral weak vector boson Z0. We compare the cross section of this process with the cross section of the lower-order process in which two quarks and one photon are produced. We find that ggγ production is unimportant in comparison with q¯qγ production except near phase-space boundaries on the Z0 resonance.
Physical Review D, Jul 1, 1980
We investigate the quark gas at finite temperatures and densities including nonperturbative effec... more We investigate the quark gas at finite temperatures and densities including nonperturbative effects in the framework of quantum chromodynamics. In our calculations we use the dilute-gas approximation for the thermodynamics of the finite-temperature instanton gas. For the suppression of large-scale instantons we consider the color-charge screening. The nonperturbative results can be compared directly from our numerical evaluations with those of the perturbation calculations.
Ijmpa, 1995
We review the relationship between the pion decay constant fπ, the chiral symmetry restoration te... more We review the relationship between the pion decay constant fπ, the chiral symmetry restoration temperature Tc and the phenomenology of low energy chiral symmetry breaking in view of the recent confirmation of the existence of a sigma meson with a mass of 600-700 MeV.
We investigate the correspondence between a perfect fluid and a scalar field and show a possible ... more We investigate the correspondence between a perfect fluid and a scalar field and show a possible way of expressing thermodynamic quantities such as entropy, particle number density, temperature and chemical potential in terms of the scalar field phi and its kinetic term X. We prove a theorem which relates isentropy with purely kinetic Lagrangian. As an application, we study the evolution of the gravitational potential in cosmological perturbation theory.
Nuclear Physics B, Oct 1, 1981
We investigate the instanton paramagnetic medium at finite temperature. By analyzing the equation... more We investigate the instanton paramagnetic medium at finite temperature. By analyzing the equation of state we show explicitly the presence of both first- and second- order phase transitions. Within the known framework of the mean field type of approximations we also include the effects of large-scale vacuum fluctuations. The numerical results are compared to other approaches to this problem in quantum chromodynamics at finite temperature.
Physics Letters B, Nov 5, 1979
We investigate the nonperturbative effects in QCD at finite density and temperature. Within the d... more We investigate the nonperturbative effects in QCD at finite density and temperature. Within the dilute gas approximation we estimate explicitly these effects at high densities. These results are compared with perturbation calculations.
Physical Review D Particles and Fields, Jul 1, 2009
We consider the prospects for dark matter/energy unification in k-essence type cosmologies. Gener... more We consider the prospects for dark matter/energy unification in k-essence type cosmologies. General mappings are established between the k-essence scalar field, the hydrodynamic and braneworld descriptions. We develop an extension of the general relativistic dust model that incorporates the effects of both pressure and the associated acoustic horizon. Applying this to a tachyon model, we show that this inhomogeneous “variable Chaplygin gas” does evolve into a mixed system containing cold dark matter like gravitational condensate in significant quantities. Our methods can be applied to any dark energy model, as well as to mixtures of dark energy and traditional dark matter.
Physical review D: Particles and fields
ABSTRACT
Physical Review D
ABSTRACT
Physical Review D
ABSTRACT