共查询到20条相似文献,搜索用时 15 毫秒
1.
Alessandro Giuliani 《Journal of statistical physics》2009,134(5-6):1059-1070
We consider a system of classical Heisenberg spins on a cubic lattice in dimensions three or more, interacting via the dipole-dipole interaction. We prove that at low enough temperature the system displays orientational long range order, as expected by spin wave theory. The proof is based on reflection positivity methods. In particular, we demonstrate a previously unproven conjecture on the dispersion relation of the spin waves, first proposed by Fröhlich and Spencer, which allows one to apply infrared bounds for estimating the long distance behavior of the spin-spin correlation functions. 相似文献
2.
Erhard T. K. Haupt 《光谱学快报》2013,46(9):1091-1097
4,6JHH-long range couplings in an estrone-type molecule are observed and demonstrated to be helpful for the complete proton chemical shift assignment. 相似文献
3.
已有的和建造中的对撞机的运行常常被束-束相互作用引起的非线性效果所限制,特别是大流强的束流,如正在研究中的BEPC多束团对撞方案,BEPCⅡ上的束-束相互作用非常复杂,束团除了在南对撞点正撞外,还在环上其余11个位置有远程相互作用,本文计算了远程束-束相互作用的频移和频散。 相似文献
4.
We consider ferromagnetic Ising systems where the interaction is given by the sum of a fixed reference potential and a Kac
potential of intensity λ≥0 and scaling parameter γ>0$. In the Lebowitz Penrose limit γ→0+$ the phase diagram in the (T,λ) positive quadrant is described by a critical curve λmf(T), which separates the regions with one and two phases, respectively below and above the curve. We prove that if $λ>mf(T), i.e. above the curve, there are at least two Gibbs states for small values of γ. If instead λ<λmf(T) and if the reference Gibbs state (i.e. without the Kac potential) satisfies a mixing condition at the temperature T, then, at the same temperature the full interaction (i.e. with also the Kac potential) satisfies the Dobrushin Shlosman
uniqueness condition for small values of γ so that there is a unique Gibbs state.
Received: 9 April 1996 / Accepted: 26 November 1996 相似文献
5.
气体检测中需选用最优波数范围来进行气体光谱的定量分析。传统波数范围的选取主要根据标准光谱的特征吸收,存在抗干扰性较差、在实际情况中容易出现较大偏差的问题。文章将二维相关红外光谱方法用于气体检测,对SO2,NO及NO2进行光谱结构分析和光谱信息发掘,以确定最优定量波数区间。以浓度值为微扰量,用含不同浓度某气体成分的一组红外吸收光谱,做二维相关得到SO2,NO及NO2的动态光谱,利用同步相关光谱和异步相关光谱来分析对气体浓度变化最敏感的波数区间,确定了被测气体定量分析的优选波数范围,包括一系列独立的波数点和连续的波数区间。作为一种新颖的最优定量波数区间选取方法,其得到的结论与理想的分析谱带选取的结果相吻合,证明了此方法的有效性。 相似文献
6.
Hadi Salehi 《General Relativity and Gravitation》2003,35(9):1679-1690
For an effective treatment of the evaporation process of a large black hole the problem concerning the role played by the fluctuations of the (vacuum) stress tensor close to the horizon is addressed. We present arguments which establish a principal relationship between the outwards fluctuations of the stress tensor close to the horizon and quantities describing the onset of the evaporation process. This suggest that the evaporation process may be described by a fluctuation-dissipation theorem relating the noise of the horizon to the black hole evaporation rate. 相似文献
7.
The theoretic renormalization-group approach is applied to the study of the critical behavior of the ddimensional Ising model with long-range correlated quenched impurities, which has a power-like correlations r^-(d-p). The asymptotic scaling law is studied in the framework of the expansion in e = 4 - d. In d ~ 4, the dynamic exponent z .is calculated up to the second order in p with ρ= O(ε^1/2). The shape function is obtained in one-loop calculation. When d = 4, the logarithmic corrections to the critical behavior are found. The finite size effect on the order parameter relaxation rate is also studied. 相似文献
8.
The theoretic renormalization-group approach is applied to the study of the critical behavior of the ddimensional Ising model with long-range correlated quenched impurities, which has a power-like correlations r-(d-ρ).The asymptotic scaling law is studied in the framework of the expansion in ε = 4 - d. In d < 4, the dynamic exponent z .is calculated up to the second order in ρ with ρ = O(ε1/2). The shape function is obtained in one-loop calculation.When d = 4, the logarithmic corrections to the critical behavior are found. The finite size effect on the order parameter relaxation rate is also studied. 相似文献
9.
10.
Graham J. Harris Neesha Patel Bernard J. Rawlings T. J. Norwood 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(2):504-509
Measurement of nuclear Overhauser enhancement is one of the mainstays of structural studies of molecules in solution. Measurements, particularly over long distances, are often compromised by spin diffusion. A robust and accurate method for measuring nuclear Overhauser enhancements that are largely free of spin diffusion effects is presented. The effects of using imperfect radiofrequency pulses are considered and experimental data are presented for Amphotericin B. 相似文献
11.
N. Crampé 《Letters in Mathematical Physics》2006,77(2):127-137
We study new interactions between degrees of freedom for Calogero, Sutherland and confined Calogero spin models. These interactions are encoded by the generators of the Lie algebra so(N) or sp(N). We find the symmetry algebras of these new models: the half-loop algebra based on so(N) or sp(N) for the Calogero models and the Yangian of so(N) or sp(N) for the two types of other models. Surprisingly, these symmetry occur only for a specific value of the coupling constant.Dedicated to my PhD supervisor and friend D. Arnaudon. 相似文献
12.
Shinsho Oryu 《Few-Body Systems》2013,54(1-4):283-286
The Fourier transform of the Born term of the AGS equation in the NNπ-system generates an energy-dependent Yukawa-type local NN-quasi-potential. An appropriate average with respect to energy suggests a variety of local NN-potentials with different ranges: 1/r(r + a) m?1 (for 2 ≤ m) where in the long range region it becomes 1/r m , while in the short range region the Yukawa-type potential e ?(m?1)r/a /r results. Therefore, one finds that the Yukawa potential is automatically accompanied by an additional longer range interaction 1/r m . For m = 2, the potential 1/r 2 produces Efimov-like bound states in the deuteron spectra. The m = 6, 7 cases lead to the Van der Waals potential. 相似文献
13.
14.
描述了一种用于中能重离子核反应实验研究的大动态范围双维位置灵敏多叠层探测系统.该探测系统由纵向电场气体电离室(IC)、大面积双维位置灵敏穿透型Si探测器(PSSD)、大面积Si光敏二极管(SPD)和用光二极管读出的16单元CsI(Tl)闪烁体探测器阵列组成.用a放射源Am(5.486MeV)测得的IC、PSSD的能量分辨率分别为3%和2.6%.在25MeV/u 40Ar诱发的核反应中,探测到的a粒子的能量动态范围为2—130MeV,此探测系统清楚地分辨出Z=2到Z=21的元素,对Z=18的Z分辨本领Z/△Z≈44.5,位置分辨为0.86±0.03mm(FWHM). 相似文献
15.
Marzio Cassandro Immacolata Merola Pierre Picco Utkir Rozikov 《Communications in Mathematical Physics》2014,327(3):951-991
We consider the phase separation problem for the one-dimensional ferromagnetic Ising model with long-range two-body interaction, J(n) = n ?2+α , where ${n\in {\rm {I\!N}}}$ denotes the distance of the two spins and ${\alpha \in [0,\alpha_+[}$ with α + = (log 3)/(log 2) ?1. We prove that when α = 0 the localization of the phase separation fluctuates macroscopically with a non-uniform explicit limiting law, while when 0 < α < α + the macroscopic fluctuations disappear and mesoscopic ones appear with a gaussian behavior when conveniently scaled. The mean magnetization profile is also given. 相似文献
16.
We study long range random Ising models and develop modified high temperature and strong magnetic field expansions that give
decay of truncated correlation functions and uniqueness of Gibbs states, in spite of the presence of Griffiths' singularities.
Received: 30 September 1996 / Accepted: 18 February 1997 相似文献
17.
Raúl Toral 《Journal of statistical physics》2004,114(5-6):1393-1398
It will be given analytical and numerical evidence supporting that the X-Y model yields an extensive, i.e., proportional to the number of degrees of freedom N, internal energy U for any value of the interaction range. 相似文献
18.
One bond 13C–1H couplings have been extensively studied and their magnitudes explained on the basis of two contributing factors, namely the percentage “s” character of the bond1 and the carbon Z value, or effective nuclear charge2. To date however, little has been reported on 13C couplings over more than one bond, the main reason being the previous experimental difficulties in measuring these small couplings. 相似文献
19.
Marzio Cassandro Enza Orlandi Pierre Picco 《Communications in Mathematical Physics》2009,288(2):731-744
We study one–dimensional Ising spin systems with ferromagnetic, long–range interaction decaying as n
−2+α
, , in the presence of external random fields. We assume that the random fields are given by a collection of symmetric, independent,
identically distributed real random variables, gaussian or subgaussian. We show, for temperature and strength of the randomness
(variance) small enough, with IP = 1 with respect to the random fields, that there are at least two distinct extremal Gibbs measures.
Supported by: GDRE 224 GREFI-MEFI, CNRS-INdAM. P.P was also partially supported by INdAM program Professori Visitatori 2007;
M.C and E.O were partially supported by Prin07: 20078XYHYS. 相似文献
20.
Systems with long range interactions in general are not additive, which can lead to an inequivalence of the microcanonical and canonical ensembles. The microcanonical ensemble may show richer behavior than the canonical one, including negative specific heats and other non-common behaviors. We propose a classification of microcanonical phase transitions, of their link to canonical ones, and of the possible situations of ensemble inequivalence. We discuss previously observed phase transitions and inequivalence in self-gravitating, two-dimensional fluid dynamics and non-neutral plasmas. We note a number of generic situations that have not yet been observed in such systems. 相似文献