共查询到20条相似文献,搜索用时 31 毫秒
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N. Laflorencie H. Rieger 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,40(2):201-207
In this paper we study the localization transition induced by the disorder in random antiferromagnetic spin-
chains. The results of numerical large scale computations are presented for the XX model using its free fermions representation. The scaling behavior of the spin stiffness is investigated for various disorder strengths. The disorder dependence of the localization length is studied and a comparison between numerical results and bosonization arguments is presented. A non trivial connection between localization effects and the crossover from the pure XX fixed point to the infinite randomness fixed point is pointed out.Received: 6 February 2004, Published online: 12 August 2004PACS:
75.10.Jm Quantized spin models - 75.40.Mg Numerical simulation studies - 05.70.Jk Critical point phenomena - 75.50.Lk Spin glasses and other random magnets 相似文献
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Exact solution of the one-dimensional spin-\frac{\mathsf 3}{\mathsf 2} Ising model in magnetic field
A. Avella F. Mancini 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(4):527-539
In this paper, we study the Ising model with general spin S in
presence of an external magnetic field by means of the equations of
motion method and of the Green's function formalism. First, the
model is shown to be isomorphic to a fermionic one constituted of
2S species of localized particles interacting via an intersite
Coulomb interaction. Then, an exact solution is found, for any
dimension, in terms of a finite, complete set of eigenoperators of
the latter Hamiltonian and of the corresponding eigenenergies. This
explicit knowledge makes possible writing exact expressions for the
corresponding Green's function and correlation functions, which turn
out to depend on a finite set of parameters to be self-consistently
determined. Finally, we present an original procedure, based on
algebraic constraints, to exactly fix these latter parameters in the
case of dimension 1 and spin
. For this latter case and,
just for comparison, for the cases of dimension 1 and spin
[F. Mancini, Eur. Phys. J. B 45, 497 (2005)] and
spin 1 [F. Mancini, Eur. Phys. J. B 47, 527 (2005)],
relevant properties such as magnetization 〈S 〉 and
square magnetic moment 〈S2 〉, susceptibility and
specific heat are reported as functions of temperature and external
magnetic field both for ferromagnetic and antiferromagnetic
couplings. It is worth noticing the use we made of composite
operators describing occupation transitions among the 3 species of
localized particles and the related study of single, double and
triple occupancy per site. 相似文献
4.
Time-dependent mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques
are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The
flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using
a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices
or by a measurement of the lepton impact parameter. The combined result for the frequency of meson oscillations is
Received: 20 February 1998 / Revised version: 23 March 1998 / Published online: 12 August 1998 相似文献
5.
R. M. Godbole C. Hangst M. Mühlleitner S. D. Rindani P. Sharma 《The European Physical Journal C - Particles and Fields》2011,71(6):1-19
In this paper we investigate methods to study the $t\bar{t}$ Higgs coupling. The spin and CP properties of a Higgs boson are analysed in a model-independent way in its associated production with a $t\bar{t}$ pair in high-energy e + e ? collisions. We study the prospects of establishing the CP quantum numbers of the Higgs boson in the CP-conserving case as well as those of determining the CP-mixing if CP is violated. We explore in this analysis the combined use of the total cross section and its energy dependence, the polarisation asymmetry of the top quark and the up-down asymmetry of the antitop with respect to the top–electron plane. We find that combining all three observables remarkably reduces the error on the determination of the CP properties of the Higgs Yukawa coupling. Furthermore, the top polarisation asymmetry and the ratio of cross sections at different collider energies are shown to be sensitive to the spin of the particle produced in association with the top-quark pair. 相似文献
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J. G. Li P. J?nsson G. Gaigalas C. Z. Dong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):313-317
Hyperfine induced $1s2s\ ^1$ S $_0 \rightarrow 1s^2\ ^1$ S0 M1 transition probabilities of He-like ions have been calculated from relativistic configuration interaction wavefunctions including the frequency independent Breit interaction and QED effects. Present results for 151Eu and 155Gd are in good agreement with previous calculations [L.N. Labzowsky et al., Phys. Rev. A 63, 054105 (2001)]. Electronic data are given in terms of a general scaling law in Z that, given isotopic nuclear spin and magnetic moment, allows hyperfine induced decay rates to be estimated for any isotope. The results should be helpful for future experimental investigations on QED and parity non-conservation effects. 相似文献
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N. D. Christensen P. de Aquino N. Deutschmann C. Duhr B. Fuks C. Garcia-Cely O. Mattelaer K. Mawatari B. Oexl Y. Takaesu 《The European Physical Journal C - Particles and Fields》2013,73(10):1-23
Support for interactions of spin- $\frac{3}{2}$ particles is implemented in the FeynRules and ALOHA packages and tested with the MadGraph 5 and CalcHEP event generators in the context of three phenomenological applications. In the first, we implement a spin- $\frac{3}{2}$ Majorana gravitino field, as in local supersymmetric models, and study gravitino and gluino pair-production. In the second, a spin- $\frac{3}{2}$ Dirac top-quark excitation, inspired from compositeness models, is implemented. We then investigate both top-quark excitation and top-quark pair-production. In the third, a general effective operator for a spin- $\frac{3}{2}$ Dirac quark excitation is implemented, followed by a calculation of the angular distribution of the s-channel production mechanism. 相似文献
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In this article, we study the $\frac{1} {2}^ -$ and $\frac{3} {2}^ -$ heavy and doubly heavy baryon states $\Sigma _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi '_Q \left( {\frac{1} {2}^ - } \right)$ , $\Omega _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Omega _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Sigma _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Omega _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ and $\Omega _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ by subtracting the contributions from the corresponding $\frac{1} {2}^ +$ and $\frac{3} {2}^ +$ heavy and doubly heavy baryon states with the QCD sum rules in a systematic way, and make reasonable predictions for their masses. 相似文献
10.
A large deviation technique is used to calculate the microcanonical entropy function s(v,m) of the mean-field ϕ4-model as a function of the potential energy v and the magnetization m. As in the canonical ensemble, a continuous phase transition
is found. An analytical expression is obtained for the critical energy vc(J) as a function of the coupling parameter J. 相似文献
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Avraham Gal 《Hyperfine Interactions》2009,193(1-3):165-171
The main features of coupled-channel ${\bar K}N$ dynamics near threshold and its repercussions in few-body $\bar K$ -nuclear systems are briefly reviewed highlighting the I?=?1/2 ${\bar K}NN$ system. For heavier nuclei, the extension of mean-field calculations to multi- $\bar K$ nuclear quasibound states is discussed focusing on kaon condensation. 相似文献
14.
The Einstein-Maxwell equations for non-static charged shear-free spherically symmetric perfect fluid distribution reduce to
a second-order non-linear differential equation in the radial parameter. Several solutions of this equation have been obtained
in earlier work without considering the general requirement for physical relevance of the solutions. Generally physically
acceptable relativistic fluid models demand that the solutions satisfy the reality conditions ρ ≥ 0, p ≥ 0, ρ
r
≤ 0, etc. throughout the fluid model. In this article the expression for density gradient ρ
x
(or ρ
r
) has been utilized to produce charged shear-free relativistic fluid models with non-positive density gradient (NDG)ρ
r
≤ 0. Eventually, we have found that none of the Riccati solutions have NDG including Vaidya metric. Also, the solutions with
NDG neither possess Lie-symmetries nor Painlevé property. Further, it is observed that the solutions with NDG have no uncharged
analogue. 相似文献
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S. G. Zemlyanoi D. V. Karaivanov Yu. P. Gangrsky K. P. Marinova B. N. Markov J. Badamsambuu 《Hyperfine Interactions》2010,196(1-3):107-113
Using the method of laser-induced fluorescence in an atomic beam we have measured the hyperfine splitting constants, A and B, of the ground and excited states of the optical transition 4f 76s 2 8S $_{1/2}\to 4f^{7}$ 6s6p 6P5/2 (564.58 nm) for 151???155Eu isotopes. For all isotopes, the magnetic dipole constants of the 6P5/2 atomic level are determined to a precision better than 0.04%. The A and B constants for the ground state 8S7/2 of the radioactive 152,154,155Eu were obtained for the first time with a precision better than 0.5%. Our data along with previous ground state hyperfine structure measurements for the stable europium isotopes allow us to determine the hyperfine anomaly for mentioned Eu isotopes. 相似文献
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P. H. Y. Li R. F. Bishop 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):25
We consider coevolution of site state and network structures from different initial
substrates: a one dimensional Ising chain, a scale free network and network with
non-linear degree dependence. The dynamics is governed by a preassigned stability
parameter S, and a rewiring factor φ, that determines
whether the Ising spin at the chosen site flips or whether the site gets rewired to
another site in the system. We have observed the steady state average stability and
magnetisation for both kinds of systems to have an idea about the effect of initial
network topology. Although the average stability shows almost similar behaviour, the
magnetisation depends on the initial condition we start from. Apart from the local
dynamics, the global effect on the dynamics has also been studied. These studies show
interesting variations in the steady state values of average stability and magnetisation
for different values of S and φ, which helps in
indicating the gradual change of existing social networks. 相似文献
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R. Barate et al. 《The European Physical Journal C - Particles and Fields》2001,19(2):213-227
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Miklukho O. V. Kisselev A. Yu. Amalsky G. M. Andreev V. A. Barsov S. G. Gavrilov G. E. Zhdanov A. A. Izotov A. A. Ilyin D. S. Kozlenko N. G. Kravchenko P. V. Maysuzenko D. A. Murzin V. I. Novinskiy D. V. Shvedchikov A. V. 《Physics of Atomic Nuclei》2020,83(3):431-441
Physics of Atomic Nuclei - The secondary proton polarization and differential cross sections of the ( $$p,p^{\prime}$$ ) inelastic reaction on nuclei $${}^{9}$$ Be and $${}^{90}$$ Zr at the initial... 相似文献