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1.
P. Costa C. A. de Sousa M. C. Ruivo Yu. L. Kalinovsky 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):842-844
We study the chiral phase transition at finite T and μ
B within the framework of the SU(3) Nambu-Jona-Lasinio (NJL) model. The QCD critical end point (CEP) and the critical line at finite temperature and baryonic
chemical potential are investigated: the study of physical quantities, such as the baryon number susceptibility near the CEP,
will provide complementary information concerning the order of the phase transition. We also analyze the information provided
by the study of the critical exponents around the CEP. 相似文献
2.
S C Phatak 《Pramana》2001,57(2-3):325-335
It is expected that at very large densities and/or temperatures a quark-hadron phase transition takes place. Lattice QCD calculations
at zero baryon density indicate that the transition occurs at T
c ∼ 150–170 MeV. The transition is likely to be second order or a cross over phenomenon. Although not much is known about the
density at which the phase transition takes place at small temperatures, it is expected to occur around the nuclear densities
of few times nuclear matter density. Also, there is a strong reason to believe that the quark matter formed after the phase
transition is in colour superconducting phase. The matter densities in the interior of neutron stars being larger than the
nuclear matter density, the neutron star cores may possibly consist of quark matter which may be formed during the collapse
of supernova. Starting with the assumption that the quark matter, when formed consists of predominantly u and d quarks, we consider the evolution of s quarks by weak interactions in the present work. The reaction rates and time required to reach the chemical equilibrium are
computed here. Our calculations show that the chemical equilibrium is reached in about 10−7 seconds. Further more during the equilibration process enormous amont of energy is released and copious numbers of neutrinos
are produced. Implications of these on the evolution of supernovae will be discussed. 相似文献
3.
Chengfu Mu Pengfei Zhuang 《The European Physical Journal C - Particles and Fields》2008,58(2):271-279
We investigate the effect of the restoration of chiral symmetry on the quark potential in a quark–meson plasma by considering
meson exchanges in the two flavor Nambu–Jona-Lasinio model at finite temperature and density. There are two possible oscillations
in the chiral restoration phase; one is the Friedel oscillation due to the sharp quark Fermi surface at high density, and
the other is the Yukawa oscillation driven by the complex meson poles at high temperature. The quark–meson plasma is strongly
coupled in the temperature region 1≤T/T
c≤3, with T
c being the critical temperature of the chiral phase transition. The maximum coupling in this region is located at the phase
transition point. 相似文献
4.
Summary Most previous studies of magnetism in various compounds under extreme conditions have been conducted over a wide pressure
range at room temperature or over a wide range of cryogenic temperatures at pressures below 20 GPa (200 kbar). We present
some of the most recent studies of magnetism over an extended range of temperatures and pressures far beyond 20 GPa,i.e. in regions of pressure-temperature (P-T) space where magnetism has been largely unexplored. Recent techniques have permitted investigations of magnetism in selected
3d transition metal compounds in regions ofP-T where physical properties may be drastically modified; related effects have often been seen in selected doping studies at
ambient pressures. We present57Fe and129I M?ssbauer isotope studies covering the range 300–4 K to sub-megabar pressures in compounds such as Sr2FeO4, LaFeO3 and FeI2, representative of a broad class of 3d transition metal compounds. At ambient pressure the electronic structure of the transition metal atom in these antiferromagnetic
insulators extends from 3d
4 to 3d
6 and has a distinct influence on the pressure evolution of their magnetic properties. M?ssbauer studies of these compounds
are considered in conjunction with available structural and electrical transport data at pressure.
Paper presented at ICAME-95, Rimini, 10–16 September 1995. 相似文献
5.
We consider the presence of cosmic string-induced density fluctuations in the early universe at temperatures below the electroweak
phase transition temperature. Resulting temperature fluctuations can restore the electroweak symmetry locally, depending on
the amplitude of fluctuations and the background temperature. The symmetry will be spontaneously broken again in a given region
as the temperature drops there (for fluctuations with length scales smaller than the horizon), resulting in the production
of baryon asymmetry. The time-scale of the transition will be governed by the wavelength of fluctuation and, hence, can be
much smaller than the Hubble time. This leads to strong enhancement in the production of baryon asymmetry for a second-order
electroweak phase transition as compared to the case when transition happens due to the cooling of the universe via expansion.
For a two-Higgs doublet model (with appropriate CP violation), we show that one can get the required baryon asymmetry if fluctuations
propagate without getting significantly damped. If fluctuations are damped rapidly, then a volume factor suppresses the baryon
production, though it is still 3–4 orders of magnitude larger than the conventional case of second-order transition. 相似文献
6.
V. M. Gaba V. I. Stadnyk Z. O. Kogut R. S. Brezvin 《Journal of Applied Spectroscopy》2010,77(5):648-653
The influence of uniaxial mechanical stresses directed along the principal crystallophysical axes on refractiveindex temperature
dependences in K2ZnCl4 crystals was studied. It is established that the refractive indices ni are quite sensitive to uniaxial stresses. Significant
baric shifts of the paraphase–incommensurate–commensurate phase transition points to different temperature regions were observed,
which is due to the effect of the uniaxial stress on the K2ZnCl4 crystal structure. It is found that applying uniaxial pressure increases the value of the temperature hysteresis of the commensurate–incommensurate
phase transition. 相似文献
7.
Bouetou Bouetou Thomas Mahamat Saleh Timoleon Crepin Kofane 《General Relativity and Gravitation》2012,44(9):2181-2189
We investigate thermodynamics and phase transition of the Reissner–Nordstr?m black hole surrounded by quintessence. Using thermodynamical laws of black holes, we derive the expressions of some thermodynamics quantities for the Reissner–Nordstr?m black hole surrounded by quintessence. The variations of the temperature and heat capacity with the entropy were plotted for different values of the state parameter related to the quintessence, ω q , and the normalization constant related to the density of quintessence c. We show that when varying the entropy of the black hole a phase transition is observed in the black hole. Moreover, when increasing the density of quintessence, the transition point is shifted to lower entropy and the temperature of the black hole decreases. 相似文献
8.
We show that large fluctuations of D-mesons kinetic-energy (or momentum) distributions might be a signature of a phase transition to the Quark-Gluon Plasma (QGP).
In particular, a jump in the variance of the momenta or kinetic energy, as a function of a control parameter (temperature
or Fermi energy at finite baryon densities) might be a signature for a first-order phase transition to the QGP. This behavior
is completely consistent with the order parameter defined for a system of interacting quarks both at zero temperature (and
finite baryon densities) or at finite temperatures which shows a jump in correspondence with a first-order phase transition
to the QGP. The J/Ψ displays exactly the same behavior of the order parameter and of the variance of the D-mesons. We discuss implications for relativistic heavy-ion collisions within the framework of a transport model and possible
hints for experimental search. 相似文献
9.
I. O. Bashkin M. V. Nefedova V. G. Tissen E. G. Ponyatovskii 《Physics of the Solid State》1998,40(12):1950-1952
The pressure dependence of the superconducting transition temperature in TiD0.74 has been measured up to 30 GPa in a diamond high-pressure chamber. It is found that the deuteride TiD0.74 becomes a superconductor at pressures corresponding to the transition to the high-pressure ζ phase, with a transition temperature that increases from 4.17 to 4.43 K in the interval P=14–30 GPa. The value extrapolated to atmospheric pressure T
c
(0)=4.0 K is significantly lower than the superconducting transition temperature (T
c
=5.0 K) measured earlier in the metastable state obtained by quenching TiD0.74 under pressure. It is assumed that the significant difference of the extrapolated value from the superconducting transition
temperature in the metastable state after quenching under pressure is caused by a phase transition on the path from the stability
region of the ζ phase under pressure to the region of the metastable state at atmospheric pressure.
Fiz. Tverd. Tela (St. Petersburg) 40, 2153–2155 (December 1998) 相似文献
10.
G. V. Loseva L. I. Ryabinkina S. S. Aplesnin A. D. Balaev A. F. Bovina A. M. Vorotynov K. I. Yanushkevich 《Physics of the Solid State》1997,39(8):1267-1270
A study of the structure and electrical and magnetic properties of the VxMn1−x
S disordered system is reported. The existence of a low-temperature metal-insulator transition for Fermi-glass 0.4<x<0.5 compositions in paramagnetic phase, which is accompanied by a change in the structure and magnetic properties, has been
established. An analysis of the magnetic properties permits a conjecture that current carriers become delocalized in these
solid solutions at the metal-insulator transition temperature to form small ferromagnetically ordered regions (ferrons).
Fiz. Tverd. Tela (St. Petersburg) 39, 1428–1431 (August 1997) 相似文献
11.
We use the non-perturbative Q$
\bar Q
$
\bar Q
potential at finite temperatures derived in the Field Correlator Method to obtain binding energies for the lowest eigenstates
in the Q$
\bar Q
$
\bar Q
and QQQ systems (Q = c, b). The three-quark problem is solved by the hyperspherical method. The solution provides an estimate of the melting temperature
and the radii for the different diquark and triquark bound states. In particular we find that J/ψ and ccc ground states survive up to T − 1.3T
c
, where T
c
is the critical temperature, while the corresponding bottomonium states survive even up to higher temperature, T − 2.3T
c
. 相似文献
12.
I. Bombaci D. Logoteta P.K. Panda C. Providência I. Vidaa 《Physics letters. [Part B]》2009,680(5):448-452
We study the quark deconfinement phase transition in hot β-stable hadronic matter. Assuming a first order phase transition, we calculate the enthalpy per baryon of the hadron–quark phase transition. We calculate and compare the nucleation rate and the nucleation time due to thermal and quantum nucleation mechanisms. We compute the crossover temperature above which thermal nucleation dominates the finite temperature quantum nucleation mechanism. We next discuss the consequences for the physics of proto-neutron stars. We introduce the concept of limiting conversion temperature and critical mass Mcr for proto-hadronic stars, and we show that proto-hadronic stars with a mass M<Mcr could survive the early stages of their evolution without decaying to a quark star. 相似文献
13.
P. Castorina K. Redlich H. Satz 《The European Physical Journal C - Particles and Fields》2009,59(1):67-73
We interpret the phase structure of hadronic matter in terms of the basic dynamical and geometrical features of hadrons. Increasing
the density of constituents of finite spatial extension, by increasing the temperature T or the baryochemical potential μ, eventually “fills the box” and eliminates the physical vacuum. We determine the corresponding transition as a function of
T and μ through percolation theory. At low baryon density, this means a fusion of overlapping mesonic bags to one large bag, while
at high baryon density, hard-core repulsion restricts the spatial mobility of baryons. As a consequence, there are two distinct
limiting regimes for hadronic matter. We compare our results to those from effective chiral model studies. 相似文献
14.
Z. A. Kazei V. V. Snegirev A. S. Andreenko L. P. Kozeeva 《Journal of Experimental and Theoretical Physics》2011,113(2):245-250
The elastic properties of rare-earth cobaltites RBaCo4O7 (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80–300 K. The strong softening of the Young modulus
ΔE(T)/E
0 ≈ −(0.1–0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure
upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young
modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T
s and hysteresis ΔT
s increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in
Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite
is not a “soft” mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites
is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature
phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller. 相似文献
15.
C. Wetterich 《The European Physical Journal C - Particles and Fields》2003,29(2):251-264
We explore the possibility that QCD may undergo a phase transition as a function of the strange quark mass. This would hint
towards models with ”spontaneous color symmetry breaking” in the vacuum. For two light quark flavors we classify possible
colored quark-antiquark, diquark and gluon condensates that are compatible with a spectrum of integer charged states and conserved
isospin and baryon number. The ”quark mass phase transition” would be linked to an unusual realization of baryon number in
QCD2 and could be tested in lattice simulations. We emphasize, however, that at the present stage the Higgs picture of the vacuum
cannot predict a quark mass phase transition - a smooth crossover remains as a realistic alternative. Implications of the
Higgs picture for the high-density phase transition in QCD2 suggest that this transition is characterized by the spontaneous breaking of isospin for nuclear and quark matter.
Received: 12 March 2001 / Revised version: 2 April 2003 / Published online: 2 June 2003
RID="a"
ID="a" e-mail: C.Wetterich@thphys.uni-heidelberg.de 相似文献
16.
The specific heat of Pb2MgWO6 has been measured in the temperature interval 83–370 K. An anomaly in the specific heat associated with the phase transition
at T
0=312.8K has been discovered. The thermodynamic parameters of the structural phase transition Fm3m-Pmcn have been determined.
Fiz. Tverd. Tela (St. Petersburg) 41, 1686–1688 (September 1999) 相似文献
17.
A. D. Bozhko A. N. Vasil’ev V. V. Khovailo I. E. Dikshtein V. V. Koledov S. M. Seletskii A. A. Tulaikova A. A. Cherechukin V. G. Shavrov V. D. Buchel’nikov 《Journal of Experimental and Theoretical Physics》1999,88(5):954-962
The results of an experimental investigation of the temperature dependences of the magnetic susceptibility and resistivity
in the shape-memory ferromagnetic alloys Ni2+x
Mn1−x
Ga (x=0–0.20) are reported. A T−x phase diagram is constructed on the basis of these data. It is shown that partial substitution of Ni for Mn causes the temperatures
of the structural (martensitic) T
M
and magnetic T
C
(Curie point) phase transitions to converge. In the region where T
C
=T
M
the transition temperature increases linearly with magnetic field in the range from 0 to 10 kOe. The kinetics of a magnetic-field-induced
martensitic phase transition is investigated, and the velocities of the martensite-austenite interphase boundary during direct
and reverse transitions are measured. A theoretical model is proposed and the T−x phase diagram is calculated. It is shown that there exist concentration ranges where the magnetic and martensitic transitions
merge into a first-order phase transition. The theoretical results are in qualitative agreement with experiment.
Zh. éksp. Teor. Fiz. 115, 1740–1755 (May 1999) 相似文献
18.
Wanwimon Banlue Naratip Vittayakorn 《Applied Physics A: Materials Science & Processing》2008,93(2):565-569
The solid solution between the antiferroelectric PbZrO3 (PZ) and relaxor ferroelectric Pb(Co1/3Nb2/3)O3 (PCoN) was synthesized by the columbite method. The phase structure and thermal properties of (1−x)PZ–xPCoN, where x=0.0–0.3, were investigated. With these data, the ferroelectric phase diagram between PZ and PCoN has been established. The
crystal structure data obtained from XRD indicates that the solid solution PZ–PCoN, where x=0.0–0.3, successively transforms from orthorhombic to rhombohedral symmetry with an increase in PCoN concentration. The AFE→FE
phase transition was found in the compositions of 0.0≤x≤0.10. The AFE→FE phase transition shift to lower temperatures with higher compositions of x. The width of the temperature range of FE phase was increased with increasing amount of PCoN. It is apparent that the replacement
of the Zr4+ ion by (Co1/3Nb2/3)4+ ions would decrease the driving force for antiparallel shift of Pb2+ ions, because they interrupt the translational symmetry. This interruption caused the appearance of a rhombohedral ferroelectric
phase when the amount of PCoN was more than 10 mol%. 相似文献
19.
V. B. Voronkov V. G. Golubev A. V. Medvedev A. B. Pevtsov N. A. Feoktistov N. I. Gorshkov D. N. Suglobov 《Physics of the Solid State》1998,40(8):1301-1304
Using standard low-temperature (<300 °C) plasma-enhanced chemical vapor deposition (PE CVD) technology, films of a Si(Er): H were obtained that emitted light in the neighborhood of 1.54 μm at room temperature. The Er source was the specially synthesized fluorine-containing metallorganic complex Er(HFA)3·DME where HFA=CF3C(O)CHC(O)CF3 and DME=CH3OCH2CH2OCH3, which possesses a low transition temperature to the gas phase (of order 100 °C) at working pressures (0.1–0.5 Torr) for
the PE CVD method. Distinctive features of the photoluminescence spectrum of a-Si(Er):H were investigated in the range 0.5–1.7 μm for T=77 and 300 K. The presence of photoconductivity in the synthesized films is evidence of their satisfactory electronic quality.
Fiz. Tverd. Tela (St. Petersburg) 40, 1433–1436 (August 1998) 相似文献
20.
L. Álvarez-Gaumé P. Basu M. Mariño S.R. Wadia 《The European Physical Journal C - Particles and Fields》2006,48(2):647-665
In this paper we discuss the black hole–string transition of the small Schwarzschild black hole of AdS
5×S5 using the AdS/CFT correspondence at finite temperature. The finite temperature gauge theory effective action, at weak and strong coupling, can be expressed entirely in terms of constant Polyakov lines which are SU(N) matrices. In showing this we have taken into account that there are no Nambu–Goldstone modes associated with the fact that the 10-dimensional black hole solution sits at a point in S5. We show that the phase of the gauge theory in which the eigenvalue spectrum has a gap corresponds to supergravity saddle points in the bulk theory. We identify the third order N=∞ phase transition with the black hole–string transition. This singularity can be resolved using a double scaling limit in the transition region where the large N expansion is organized in terms of powers of N-2/3. The N=∞ transition now becomes a smooth crossover in terms of a renormalized string coupling constant, reflecting the physics of large but finite N. Multiply wound Polyakov lines condense in the crossover region. We also discuss the implications of our results for the resolution of the singularity of the lorenztian section of the small Schwarzschild black hole. 相似文献