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1.
Yu. A. Simonov 《Physics of Atomic Nuclei》2007,70(1):44-52
The 3d gluodynamics which governs the large-T quark—gluon plasma is studied in the framework of the field correlator method. Field correlators and spacial string tension
are derived through the gluelump Green’s functions. The glueball spectrum is calculated both in C = −1 as well as in C = +1 sectors, and multigluon bound states in the form of “gluon rings” and “gluon stars” are computed explicitly. Good overall
agreement with available lattice data is observed.
The text was submitted by the author in English. 相似文献
2.
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
3.
Pairing symmetry in oxypnictides, a new family of multiband high-T
c
superconductors, is partially imposed by the positions of multiple Fermi pockets, which itself can give rise to new order
parameters, such as s
+,− states or the state of the symmetry. Other pairing states may appear on small pockets for long-range interactions, but they are expected to be sensitive
to defects. We identify the competing antiferromagnetic order with the triplet exciton transition in the semimetallic background
and discuss whether its coexistence with superconductivity explains the doping dependence of T
c
.
The text was submitted by the authors in English. 相似文献
4.
E. Shuryak 《The European Physical Journal C - Particles and Fields》2005,43(1-4):23-30
Dramatic changes had occurred with our understanding of quark-gluon plasma, which is now believed to be rather strongly coupled. One set of questions is what is its internal structure: at the moment the best answer seem to be a liquid made of binary bound states. Another set of questions is how to probe it, especially using hard probes of the main interest to this meeting. Three suggestions to be discussed are (i) the ionization losses related to new bound states; (ii) the “conical flow” from quenched jets; (iii) possible new peaks in the dilepton spectra, corresponding to vector mesons above Tc.Arrival of the final proofs: 15 March 2005PACS:
12.38.Mh, 25.75.-q 相似文献
5.
Deconfinement phase transition due to the disappearance of confining colorelectric field correlators is described using a
nonperturbative equation of state. The resulting transition temperature T
c
(μ) at any chemical potential μ is expressed in terms of the change of the gluon condensate ΔG
2 and absolute value of the Polyakov loop L
fund(T
c
), which is known from the lattice and analytic data, and is in good agreement with the lattice data for ΔG
2 ≈ 0.0035 GeV4; e.g., T
c
(0) = 0.27, 0.19, and, 0.17 GeV for n
f
= 0, 2, and 3, respectively.
The text was submitted by the authors in English. 相似文献
6.
Isothermal remanent magnetization decay,M
r(t), and ‘in-field’ growth of zero-field-cooled magnetization,M
ZFC(t), with time have been measured over four decades in time at temperatures ranging from 0.25T
c to 1.25T
c (whereT
c is the Curie temperature, determined previously for the same sample from static critical phenomena measurements) for a nearly
ordered intermetallic compound Ni3Al, which is an experimental realization of a three-dimensional (d = 3) ferromagnet with weak quenched random-exchange disorder. None of the functional forms ofM
r(t) predicted by the existing phenomenological models of relaxation dynamics in spin systems with quenched randomness, but only
the expressions
and
closely reproduce such data in the present case. The most striking features of magnetic relaxation in the system in question
are as follows: Aging effects are absent in bothM
r
t andM
ZFC(t) at all temperatures in the temperature range covered in the present experiments. A cross-over in equilibrium dynamics from
the one, characteristic of a pured = 3 ferromagnet with complete atomic ordering and prevalent at temperatures away from Tc, to that, typical of ad = 3 random-exchange ferromagnet, occurs asT → Tc. The relaxation times τ1(T)(τ1
′(T)) and τ2(T)(τ2
′(T)) exhibit logarithmic divergence at critical temperatures
and
;
and
both increase with the external magnetic field strength,H, such that at any given field value,
. The exponent characterizing the logarithmic divergence in τ
1
′
(T) and τ
2
′
T possesses a field-independent value of ≃16 for both relaxation times. Of all the available theoretical models, the droplet
fluctuation model alone provides a qualitative explanation for some aspects of the present magnetic relaxation data 相似文献
7.
We propose the enhancement of Λ
c yield in heavy ion collisions at RHIC and LHC as a novel signal for the existence of diquarks in the strongly coupled quark-gluon
plasma produced in these collisions as well as in the Λ
c
. Assuming that stable bound diquarks can exist in the quark-gluon plasma, we argue that the yield of Λ
c would be increased by two-body collisions between [ud] diquarks and c quarks, in addition to normal three-body collisions among u, d and c quarks. A quantitative study of this effect based on the coalescence model shows that including the contribution of diquarks
to Λ
c
production indeed leads to a substantial enhancement of the Λ
c
/D ratio in heavy ion collisions. 相似文献
8.
O. I. Piskounova 《Physics of Atomic Nuclei》2007,70(6):1107-1109
Predictions were made for asymmetry between production spectra of Λ0 and
at the energy of LHC experiments. The value of A(s) should be situated in the corridor between two curves calculated in the quark-gluon string model with two possible values
of intercept α
SJ(0) = 0.5 and 0.9. Both curves describe the asymmetries measured at lower energies up to RHIC experiments. The data of the
H1 experiment can be fitted only with α
SJ(0) = 0.9.
The text was submitted by the author in English. 相似文献
9.
Summary Energy spectra and zenith-angle distributions of cosmic-ray muons, neutrinos and antineutrinos of prompt generation for energy
interval (1÷106) TeV are calculated. For calculations of differential cross-sections of D±, D0,
0 and Λc production inNN and πN interactions the recombination quark-parton model (RQPM) is used. Accounting of nuclear effects is done by using the additive
quark model and the optical model of nucleus. Detailed comparison of results obtained in RQPM with corresponding predictions
of quark-gluon string model (MQGS) is carried out. Dynamics of semi-leptonic D- and Λc and energy losses of muons in the atmosphere are taken into account. Calculations of hadronic cascades in the atmosphere
are done with accounting of growth with energy of total inelastic hadron-nucleus cross-sections, steepening of primary cosmic-ray
spectrum and processes of pion regeneration. The comparison of our calculations with experimental data and with calculations
of other authors is given. 相似文献
10.
A novel model system is proposed for the study of superconductor-insulator transitions that is a regular lattice whose each
link consists of a Josephson-junction chain of N ≫ 1 junctions in sequence. The theory of such an array is developed for the case of semiclassical junctions with the Josephson
energy E
J
larger compared to the Coulomb energy E
C
= e
2/2C of the junctions. An exact duality transformation is derived that transforms the Hamiltonian of the proposed model into a
standard Hamiltonian of a JJ array. The nature of the ground state is controlled (in the absence of random offset charges)
by the parameter q ≈ N
2 exp
with the superconductive state corresponding to small q < q
c
. The values of q
c
are calculated for magnetic frustrations f = 0 and f = 1/2. The temperature of the superconductive transition T
c
(q) and q < q
c
is estimated for the same values of f. In the presence of strong random offset charges, the T = 0 phase diagram is controlled by the parameter
; the critical value
and the critical temperature
at zero magnetic frustration are estimated.
The text was submitted by the authors in English. 相似文献
11.
Summary The crystal size in accretions grown in an icing wind tunnel at ambient temperatures −18≥T
a
≥−27°C and different substrate temperatureT
s
<0°C is studied. For constantT
s
the mean area
of crystal sections shows an approximately exponential dependence onT
a
which may be written as
, where ΔT≃−T
a
represents the droplet supercooling. On the other hand, for fixedT
a
, the crystal size is observed to decrease markedly withT
s
. By considering previous results on the orientation of crystals forming the accretions, it is shown that the value of the
mean angle
formed by the crystalc-axis with the growth direction depends as well both onT
a
andT
s
. The exponential dependence of
andT
a
and the observed correspondence between the behaviour of
and
are correlated with a nucleation mechanism, accompanied by a process of orientation selection, which would be responsible
of both the crystal size and the orientation. The application of the crystal structure analysis to the determination of the
growth conditions of hailstones is discussed.
To speed up publication, the authors of this paper has agreed to not receive the proofs for correction.
Comisión Nacional de Energía Atómica and Consejo Nacional de Investigaciones Científicas y Técnicas. 相似文献
Riassunto Si studia la dimensione di un cristallo in accrezioni cresciute in una galleria a vento congelante a temperature ambienti −18≥T a ≥−27 °C e diversa temperatura di substratoT s <0 °C. PerT s costante, l’area media delle sezioni di cristallo mostra una dipendenza daT a approssimativamente esponenziale che potrebbe essere scritta così: , dove ΔT≃−T a rappresenta il superraffreddamento della gocciolina. D’altra parte, perT a fisso, si osserva che la dimensione del cristallo decresce marcatamente conT s . Considerando precedenti risultati sull’orientamento dei cristalli che formano le accrezioni, si mostra che anche il valore dell’angolo medio formato dall’assec del cristallo con la direzione di accrescimento dipende sia daT a che daT s . La dipendenza esponenziale di daT a e la corrispondenza osservata tra il comportamento di e di sono collegate con il meccanismo di nucleazione, accompagnato da un processo di selezione dell’orientamento, che dovrebbe essere responsabile sia della dimensione che dell’orientamento del cristallo. Si discute l’applicazione dell’analisi della struttura del cristallo alla determinzione delle condizioni di accrescimento dei chicchi di grandine.
To speed up publication, the authors of this paper has agreed to not receive the proofs for correction.
Comisión Nacional de Energía Atómica and Consejo Nacional de Investigaciones Científicas y Técnicas. 相似文献
12.
Dilepton production rates in nuclear collisions are calculated in order to study their sensitivity to the quark-gluon plasma and to the hadronic phases. This treatment differs from previous work on the subject in two respects: The width of the rho-meson, being exchanged in annihilation, is made temperature dependent, thus taking into account resonance melting as the critical deconfinement temperatureT
d
is approached. Secondly, we study in addition to the standard scenario where chiral symmetry restoration and deconfinement occur at the same temperature (T
c
=T
d
), an alternative possibility where deconfinement preceeds chiral symmetry restoration (T
d
T
c
). Results differ substantially from those obtained assuming a temperature independent rho-meson width, andT
c
=T
d
. 相似文献
13.
P. Huovinen 《The European Physical Journal A - Hadrons and Nuclei》2008,37(1):121-128
We study the effect of separate chemical and kinetic freeze-outs to the ideal hydrodynamical flow in Au + Au collisions at
RHIC ( energy). Unlike earlier studies we explore how these effects can be counteracted by changes in the initial state of the hydrodynamical
evolution. We conclude that the reproduction of pion, proton and antiproton yields necessitates a chemical freeze-out temperature
of T ≈ 150MeV instead of T = 160–170 MeV motivated by thermal models. Contrary to previous reports, this lower temperature makes it possible to reproduce
the p
T spectra of hadrons if one assumes very small initial time, τ
0 = 0.2 fm/c. However, the p
T differential elliptic flow, v
2(p
T) remains badly reproduced. This points to the need to include dissipative effects (viscosity) or some other refinement to
the model. 相似文献
14.
The process of baryon production in Kp collisions at high energies is considered in the framework of the quark-gluon string model. The contribution of the string-junction
mechanism to the strange-baryon production is analyzed. The results of numerical calculations are in reasonable agreement
with the data on inclusive spectra of p, Λ,
and on the
/Λ asymmetry. The predictions for inclusive spectra and production asymmetry of Ξ and Ω baryons are presented.
The text was submitted by the authors in English. 相似文献
15.
Z. A. Kazei N. P. Kolmakova A. A. Sidorenko L. V. Takunov 《Physics of the Solid State》1998,40(9):1513-1515
The thermal expansion anomalies in TbVO4 due to the cooperative Jahn-Teller effect were studied experimentally and theoretically. Characteristic magnetoelastic anomalies
were observed in the curves of Δa/a and Δc/c of the cell parameters at T<T
c. Calculations of the magnetoelastic contribution to Δa/a and Δc/c from fully symmetric
and
and low-symmetry ɛδ modes were performed using the general crystal-field formalism, and the values of the magnetoelastic coefficient B
δ were obtained from spectroscopic and spontaneous-deformation data. It is shown that the thermal expansion of TbVO4 in both the tetragonal and orthorhombic phases can be described well on the basis of a general model based on a single set
of interaction parameters.
Fiz. Tverd. Tela (St. Petersburg) 40, 1663–1666 (September 1998) 相似文献
16.
E.V. Komarov 《Annals of Physics》2008,323(5):1230-1246
The vacuum-driven nonperturbative factors Li for quark and gluon Green’s functions are shown to define the nonperturbative dynamics of QGP in the leading approximation. EoS obtained recently in the framework of this approach is compared in detail with known lattice data for μ = 0 including P/T4, ε/T4, . The basic role in the dynamics at T ? 3Tc is played by the factors Li which are approximately equal to the modulus of Polyakov line for quark Lfund and gluon Ladj. The properties of Li are derived from field correlators and compared to lattice data, in particular the Casimir scaling property follows in the Gaussian approximation valid for small vacuum correlation lengths. Resulting curves for P/T4, ε/T4, are in a reasonable agreement with lattice data, the remaining difference points out to an effective attraction among QGP constituents. 相似文献
17.
The mass spectrum of dimuons produced from the matter in the central region of rapidity in ultra-relativistic heavy-ion collisions
is calculated in accordance with Bjorken’s recently proposed model for relativistic heavy-ion collisions. The matter in this
central region is assumed to consist of a deconfined quark-gluon plasma phase and a pionized phase. Distinct enhancements
of the dimuon mass spectrum below 500 MeV, due to the quark-gluon phase, are predicted for a deconfinement phase-transition
temperatureT
c<200 MeV. 相似文献
18.
(001)YBa2Cu3O7−δ
epitaxial films were prepared by laser ablation on
surface. A thin (001)CeO2 or (111)CeO2 buffer layer was deposited between the substrate and the superconductor film to reduce their chemical interaction. In the
initial stages of CeO2 buffer formation, its orientation depended strongly on the intensity of cerium ion interaction with oxygen. Epitaxial growth
of (001)YBa2Cu3O7−δ
films was achieved both on
and
. The T
c temperature of epitaxial (001)YBa2Cu3O7−δ
films was within 88–90 K, and the current J
c at 77 K was in excess of 106 A/cm−2.
Fiz. Tverd. Tela (St. Petersburg) 40, 205–208 (February 1998) 相似文献
19.
20.
V. P. Mikhal’chenko 《Physics of the Solid State》2010,52(7):1549-1558
The effective Debye temperatures Θeff determined for solids by different physical methods have been analyzed and compared. Attention has been focused on the original
parameter of the Debye theory of heat capacity, i.e., the translational calorimetric Debye temperature Θ
c
t
(0), and the X-ray Debye temperature Θ
x
in the framework of the Debye-Waller theory for the C60 fullerite. It has been established that the true Debye law T
3 is satisfied for the C60 fullerite over a very narrow range of temperatures: 0.4 K ≤ T ≤ 1.8 K. For this reason, the experimental Debye temperatures Θ
c
t
(0) obtained for the C60 fullerite by different authors in the range T > 4.2 K are characterized by a large scatter (by a factor of ∼5). It has been revealed that the value Θ
c
t
(0) = 77.12 K calculated in this paper with the use of the six-term Betts formula from the harmonic elastic constants $
\tilde C_{ijkl}
$
\tilde C_{ijkl}
of the C60 single crystal in the limit T = 0 K is closest to the true Debye temperature. It has been demonstrated using the method of equivalent moments that the
real spectral frequency distribution of translational lattice vibrations g(ω) for the C60 fullerite deviates from a parabolic distribution. The effective Debye temperatures Θeff involved in applied problems of thermodynamics of crystals and elastic scattering of different radiations from lattice vibrations
have been determined. The quantitative measure of anharmonicity of translational and librational lattice vibrations of the
C60 fullerite has been determined. This has made it possible to empirically evaluate the lattice thermal conductivity κ of the
C60 fullerite at T ≈ 300 K: κ(300) = 0.80 W (m/K), which is in good agreement with the experimental thermal conductivity κexp = 0.78 W (m/K) at T ≈ 250 K. 相似文献