Výsledky vyhľadávania
Názov Hybrid model with viscous relativistic hydrodynamics: a role of constraints on the shear-stress tensor Aut.údaje A. S. Khvorostukhin ... [et al.] Autor Khvorostukhin A. S. (34%)
Spoluautori Kolomeitsev Evgeni E. 1970- (33%) UMBFP06 - Katedra fyziky
Toneev V. D. (33%)
Zdroj.dok. The European Physical Journal A : Hadrons and Nuclei. Vol. 57, no. 10 (2021), pp. 294-1-294-25. - New York : Springer Nature, 2021 Kľúč.slová relativistic hydrodynamics heavy ion collisions viscosity Form.deskr. články - journal articles Jazyk dok. angličtina Krajina Nemecko Anotácia We present the hybrid model connecting the parton–hadron–string dynamic model (PHSD) and a hydrodynamic model taking into account shear viscosity within the Israel–Stewart approach. The numerical scheme, initialization, and particlization procedure are discussed in detail. The performance of the code is tested on the pion and proton rapidity and transverse mass distributions calculated for Au + Au and Pb+Pb collisions at AGS–SPS energies. The influence of the switch time from transport to hydro models, the viscous parameter, and freeze-out time are discussed. Since the applicability of the Israel–Stewart hydrodynamics assumes the perturbative character of the viscous stress tensor, πμν, which should not exceed the ideal energy–momentum tensor, T μν id , hydrodynamical codes usually rescale the shear stress tensor if the inequality πμν T μν id is not fulfilled in some sense. There are several conditions used in the literature and we analyze in detail the influence of different conditions and values of the cut-off parameter on observables.We show that the form of the corresponding condition plays an important role in the sensitivity of hydrodynamic calculations to the viscous parameter – a ratio of the shear viscosity to the entropy density, η/s. It is shown that the constraints used in the vHLLE and MUSIC models give the same results for the observables.With these constraints, the rapidity distributions and transverse momentum spectra are most sensitive to a change of the η/s ratio. We demonstrate that these constraints do not guarantee that each element of the πμν tensor is smaller than the corresponding element T μν id . As an alternative, a strict condition is used. When applied it reduces the sensitivity of the proton and pion momentum distributions to the viscosity parameter. We performed global fits of the rapidity and transverse mass distributions of pion and protons. It was also found that η/s as a function of the collision energy monotonically increases from Elab = 6 AGeV up to Elab = 40 AGeV and saturates for higher SPS energies. We observe that it is difficult to reproduce simultaneously pion and proton rapidity distribution within our model with the present choice of the equation of state without a phase transition. URL Link na plný text Kategória publikačnej činnosti ADC Číslo archívnej kópie 50708 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika 
článok
Názov Viscosity of neutron star matter and r-modes in rotating pulsars Aut.údaje E. E. Kolomeitsev, D. N. Voskresensky Autor Kolomeitsev Evgeni E. 1970- (80%) UMBFP06 - Katedra fyziky
Spoluautori Voskresensky Dmitri (20%)
Zdroj.dok. Physical Review C : Nuclear Physics. Vol. 91, no. 2 (2015), pp. [1-35]. - Maryland : American Physical Society, 2015 Kľúč.slová neutrónové hviezdy neutron stars r-modes shear viscosity bulk viscosity superconductivity superfluidity Jazyk dok. angličtina Krajina Spojené štáty Systematika 539.1 Anotácia We study viscosity of the neutron star matter and $r$-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density $n_0$ and a possibility of the pion condensation at densities above $3/,n_0$ are included. The neutron-neutron and proton-proton pairings are incorporated, where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one pion exchange, and some other terms, such as the novel phonon contribution in the 1S$_0$ superfluid neutron phase, and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the $r$-modes, the term from the two-nucleon medium modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to $4/,n_0$, but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to $5/,n_0$ (corresponding to the star mass $M/simeq 1.9 M_{/odot}$). Computed with account of in-medium effects, the frequency boundary of the $r$-mode stability for the stars with the mass $/gsim 1.8 M_{/odot}$ proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in X-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value Kategória publikačnej činnosti ADC Číslo archívnej kópie 32975 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika 
nerozpoznaný
Názov Mechanism of r-mode stability in young rapidly rotating pulsars Aut.údaje E. E. Kolomeitsev, D. N. Voskresensky Autor Kolomeitsev Evgeni E. 1970- (50%) UMBFP06 - Katedra fyziky
Spoluautori Voskresensky Dmitri (50%)
Zdroj.dok. The European Physical Journal A : Hadrons and Nuclei. Vol. 50, no. 12 (2014), pp. [1-5]. - Berlin : Springer, 2014 Kľúč.slová r-modes viscosity neutron stars young pulsars Jazyk dok. angličtina Krajina Nemecko Systematika 53 Anotácia We demonstrate that stability of r-modes in young rapidly rotating pulsars might be explained if one takes into account strong medium modifications of the nucleon-nucleon interaction because of the softening of pionic degrees of freedom in dense nucleon matter. Presence of the efficient direct Urca processes is not required. Within our model the most rapidly rotating observed young pulsar PSR J0537-6910 should have the mass > 1.8M_sol Kategória publikačnej činnosti ADC Číslo archívnej kópie 31379 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika nerozpoznaný
Názov Freeze-out by bulk viscosity driven instabilities Aut.údaje Giorgio Torrieri, Boris Tomášik, Igor Mishustin Autor Torrieri Giorgio (70%)
Spoluautori Tomášik Boris 1972- (15%) UMBFP06 - Katedra fyziky
Mishustin Igor (15%)
Zdroj.dok. Acta Physica Polonica B. Vol. 39, no. 7 (2008), pp. 1733-1744. - Kraków : Jagellonian University, 2008 Kľúč.slová heavy ion collisions deconfinement phase transition hydrodynamics bulk viscosity freeze-out Jazyk dok. angličtina Krajina Poľsko Systematika 539 Anotácia We describe a new scenario (first introduced in [G.Torrieri, B.Tomasik and I.Mishustin, Phys. Rev. C 77, 034903 (2008)]) for freezeout in heavy ion collisions that could solve the lingering problems associated with the so-called HBT puzzle. We argue that bulk viscosity increases as $T$ approaches $T_c$. The fluid {then} becomes unstable against small perturbations, and fragments into clusters of a size much smaller than the total size of the system. These clusters maintain the pre-existing outward-going flow, as a spray of droplets, but develop no flow of their own, and hadronize by evaporation. We show that this scenario can explain HBT data and suggest how it can be experimentally tested Kategória publikačnej činnosti ADC Číslo archívnej kópie 9792 Kategória ohlasu RAJAGOPAL, Krishna - TRIPURANENI, Nilesh. Bulk viscosity and cavitation in boost-invariant hydrodynamic expansion. In Journal of high energy physics. ISSN 1029-8479, 2010, no. 3, article no. 94025.
MATEOS, David - TRANCANELLI, Diego. Anisotropic N=4 Super-Yang-Mills Plasma and Its Instabilities. In Physical review letters. ISSN 0031-9007, 2011, vol. 107, no. 10, article no. 101601.
MATEOS, David - TRANCANELLI, Diego. Thermodynamics and instabilities of a strongly coupled anisotropic plasma. In Journal of high energy physics. ISSN 1029-8479, 2011, no. 7, article no. 054.
CHANDRA, Vinod. Bulk viscosity of anisotropically expanding hot QCD plasma. In Physical review D. ISSN 1550-7998, 2011, vol. 84, no. 9, article no. 018.
Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika nerozpoznaný
Názov The hydrodynamic oscillator and its use in the investigation of chemical oscillators Súbež.n. Hydrodynamický oscilátor a jeho využitie v štúdiu chemických oscilátorov Aut.údaje Ľubica Adamčíková, Zuzana Melichová Autor Adamčíková Ľubica (50%)
Spoluautori Melichová Zuzana 1966- (50%) UMBFP08 - Katedra chémie
Zdroj.dok. Collection of Czechoslovak Chemical Communications. Vol. 57, no. 8 (1992), pp. 1621-1628. - Prague : The Czech Academy of Sciences, 1992 Kľúč.slová hydrodynamické oscilátory hydrodynamic oscillators oscilácie kmitanie - oscillation viskozita viscosity Jazyk dok. angličtina Krajina -CS Systematika 54 Kategória publikačnej činnosti ADF Číslo archívnej kópie 22425 Kategória ohlasu ORLIK, Marek. Reakcje oscylacyjne : porządek i chaos. Warszawa : Wydawnictwa naukowo-techniczne, 1996. [343] s. ISBN 83-204-1970-0.
KLEČKOVÁ, Marta - BLAŽKOVÁ, Radmila. Hydrodynamický oscilátor ve školním experimentu. In 50. sjezd chemických společností, Zlín, 8. - 11. záři 1997. Olomouc : Univerzita Palackého, 1997. ISBN 80-7067-745-7, s. 155.
Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika nerozpoznaný