共查询到20条相似文献,搜索用时 15 毫秒
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K. A. Bugaev A. I. Ivanytskyi V. V. Sagun D. R. Oliinychenko 《Physics of Particles and Nuclei Letters》2013,10(6):508-520
Here we present two explicit counterexamples to the widely spread beliefs about an exclusive role of bimodality as the first-order phase transition signal. On the basis of an exactly solvable statistical model generalizing the statistical multifragmentation model of nuclei, we demonstrate that the bimodal distributions can naturally appear both in infinite and in finite systems without a phase transition. In the first counterexample a bimodal distribution appears in an infinite system at the supercritical temperatures due to the negative values of the surface tension coefficient. In the second counterexample we explicitly demonstrate that a bimodal fragment distribution appears in a finite volume analog of a gaseous phase. In contrast to the statistical multifragmentation model, the developed statistical model corresponds to the compressible nuclear liquid with the tricritical endpoint located at one third of the normal nuclear density. The suggested parameterization of the liquid phase equation of state is consistent with the L. Van Hove axioms of statistical mechanics and it does not lead to an appearance of the nonmonotonic isotherms in the macroscopic mixed phase region which are typical for the classical models of the Van der Waals type. Peculiarly, such a way to account for the nuclear liquid compressibility automatically leads to an appearance of an additional state that in many respects resembles the physical antinuclear matter. 相似文献
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《Physics letters. A》1988,134(2):77-80
It is shown that the process of the collapse during quantum measurements is a consequence of the quantum symmetry built in the formalism: there exists a nontrivial group of symmetry under which all possible states are invariant after the measurement of the given observable. On the basis of this fact, the postulate of collapse is derived with purely group theoretical considerations. These are analogous to the ones used in Landau's problem of phase transitions. Some further analogies of the processes of the collapse and the phase transitions are discussed. 相似文献
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The criteria for the existence of a glass transition in a planar vortex array with quenched disorder are studied. Applying a replica Bethe ansatz, we obtain for self-avoiding vortices the exact quenched average free energy and effective stiffness which is found to be in excellent agreement with recent numerical results for the related random bond dimer model [C. Zeng, P. L. Leath, and T. Hwa, Phys. Rev. Lett. 83, 4860 (1999)] Including a repulsive vortex interaction and a finite vortex persistence length xi, we find that for xi-->0 the system is at all temperatures in a glassy phase; a glass transition exists only for finite xi. Our results indicate that planar vortex arrays in superconducting films are glassy at presumably all temperatures. 相似文献
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J.P. Kemp U.H.E. Hansmann Zheng Yu Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):371-374
The similarity in the thermodynamic properties of two completely different theoretical models for the helix-coil transition
is examined critically. The first model is an all-atomic representation for a poly-alanine chain, while the second model is
a minimal helix-forming model that contains no system specifics. Key characteristics of the helix-coil transition, in particular,
the effective critical exponents of these two models agree with each other, within a finite-size scaling analysis.
Received 8 December 1999 相似文献
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We suggest baryon–baryon correlations as an experimentally accessible signature for a first-order phase transition between a baryon-rich phase, like quarkyonic, and a baryon-suppressed hadronic phase in the QCD phase diagram. We examine the consequences of baryon-rich bubble formation in an expanding medium and show how the two-particle correlations vary in the transverse and longitudinal direction depending on the strength of the radial flow, the bubble temperature, and the time when the baryons are emitted. 相似文献
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P. M.C. de Oliveira S. Moss de Oliveira D. Stauffer S. Cebrat A. Pękalski 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):245-254
We discovered a dynamic phase transition induced by sexual
reproduction. The dynamics is a pure Darwinian rule applied to diploid
bit-strings with both fundamental ingredients to drive Darwin's
evolution: (1) random mutations and crossings which act in the sense of
increasing the entropy (or diversity); and (2) selection which acts in
the opposite sense by limiting the entropy explosion. Selection wins
this competition if mutations performed at birth are few enough, and
thus the wild genotype dominates the steady-state population. By slowly
increasing the average number m of mutations, however, the
population suddenly undergoes a mutational degradation precisely at a
transition point mc. Above this point, the “bad”
alleles (represented by 1-bits) spread over the genetic pool of the
population, overcoming the selection pressure. Individuals become
selectively alike, and evolution stops. Only below this point, m < mc, evolutionary life is possible.
The finite-size-scaling behaviour of this transition is
exhibited for large enough “chromosome” lengths L, through
lengthy computer simulations. One important and surprising observation
is the L-independence of the transition curves, for large L.
They are also independent on the population size. Another is that mc is near unity, i.e. life cannot be stable with much more
than one mutation per diploid genome, independent of the chromosome
length, in agreement with reality. One possible consequence is that an
eventual evolutionary jump towards larger L enabling the storage
of more genetic information would demand an improved DNA copying
machinery in order to keep the same total number of mutations per
offspring. 相似文献
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Premonitory effects manifest themselves in an ordering transition of the first kind (order) in the form of anomalously high short-range order (SRO) intensity at temperatures marginally above T c, the critical transition temperature. This intensity located at the superlattice positions of the long-range ordered (LRO) phase is often attributed to the formation of ‘heterophase fluctuations’ resembling clusters of the LRO phase. Monte Carlo simulations in a hypothetical system showing FCC-to-L12 ordering transition have been carried out here to shed some light on this phenomenon and to look into the atomic configurations that make up these fluctuations. 相似文献
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J. C. Kluyver 《Zeitschrift fur Physik C Particles and Fields》1979,2(4):351-354
If theS-meson is assumed to be a baryonium state composed of an isospin one diquark and antidiquark, it will be produced in \(\bar pp\) reactions as a mixture ofI=0 andI=1 baryonium states. The experimentally observed large ratio of the cross sections of the reactions \(\bar pp \to S \to \bar pp\) and \(\bar pp \to S^0 \to \bar nn\) is then explained on basis of quark additivity and conservation of isospin in thes-channel. The model predicts: \(\sigma (\bar pp \to S^0 \to \bar pp):\sigma (\bar pp \to S^0 \to \bar nn):\sigma (\bar pn \to S^ - \to \bar pn) = 25:1:16\) . 相似文献
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Cohen TD 《Physical review letters》2007,99(2):021602
It was recently conjectured that the ratio of the shear viscosity to entropy density eta/s for any fluid always exceeds [formula: see text]. A theoretical counterexample to this bound can be constructed from a nonrelativistic gas by increasing the number of species in the fluid while keeping the dynamics essentially independent of the species type. The question of whether the underlying structure of relativistic quantum field theory generically inhibits the realization of such a system and thereby preserves the possibility of a universal bound is considered here. Using rather conservative assumptions, it is shown here that a metastable gas of heavy mesons in a particular controlled regime of QCD provides a realization of the counterexample and is consistent with a well-defined underlying relativistic quantum field theory. Thus, quantum field theory appears to impose no lower bound on eta/s, at least for metastable fluids. 相似文献
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We use the heavy-ion phase-space exploration model to discuss the origin of the bimodality in charge asymmetry observed in nuclear reactions around the Fermi energy. We show that it may be related to the important angular momentum (spin) transferred into the quasiprojectile before secondary decay. As the spin overcomes the critical value, a sudden opening of decay channels is induced and leads to a bimodal distribution for the charge asymmetry. In the model, it is not assigned to a liquid-gas phase transition but to specific instabilities in nuclei with high spin. Therefore, we propose to use these reactions to study instabilities in rotating nuclear droplets. 相似文献
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F. A. Sidorenko R. E. Yurin 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(2):277-280
We develop a procedure to interpret the model M?ssbauer spectra (MS) of resonant nuclei in a two-component crystal with short-range
order. The procedure is describable not only by pair correlations but also by multiparticle correlations of the atomic distribution.
The results of the interpretation are used to find M?ssbauer parameters for subspectra and for certain correlation moments
that describe the short-range order. The developed approach was used to interpret the actual spectra of 57Fe in iron-chromium alloys. 相似文献
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