共查询到20条相似文献,搜索用时 31 毫秒
1.
Anders Martin-Löf 《Communications in Mathematical Physics》1973,32(1):75-92
For the Ising model with nearest neighbour interaction it is shown that the spin correlations
A
B
-
A
B
decrease exponentially asd(A, B) in a pure phase when the temperature is well belowT
c. This is used to prove that the free energyF(,h) is infinitely differentiable in and has one sided derivatives inh of all orders forh=0. The bounds are also used to prove that the central limit theorem holds for several variables such as e.g. the total energy and the total magnetization of the system, the limit distribution being gaussian with variances determined by the second derivatives ofF(,h). 相似文献
2.
We discuss stochastic Schrödinger operators and Jacobi matrices with wave functions, taking values in
l
so there are 2l Lyaponov exponents 1...l0
l+1...2l
=–1. Our results include the fact that if 1=0 on a set positive measure, thenV is deterministic and one that says that {E|exactly 2j 's are zero} is the essential support of the a.c. spectrum of multiplicity 2j.Research partially supported by USNSF under grant DMS-8416049 相似文献
3.
András Sütő 《Communications in Mathematical Physics》1987,111(3):409-415
The spectrum (H) of the tight binding Fibonacci Hamiltonian (H
mn=
m,n+1+
m+1,n
+
m,n
v(n),v(n)=
((n–1)), 1/ is the golden number) is shown to coincide with the dynamical spectrum, the set on which an infinite subsequence of traces of transfer matrices is bounded. The point spectrum is absent for any , and (H) is a Cantor set for 4. Combining this with Casdagli's earlier result, one finds that the spectrum is singular continuous for 16.On leave from the Central Research Institute for Physics, Budapest, Hungary 相似文献
4.
K. Kriŝtiaková O. Ŝauŝa J. Kriŝtiak Ŝ. Jánoŝ 《Zeitschrift für Physik B Condensed Matter》1989,75(2):197-199
We have measured the ac susceptibility of a wire with a Nb core (1.27 mm diam.) and a Cu cladding (0.37 mm thickness) atT50 K andB0.1 mG. Due to its proximity to Nb, the Cu becomes fully superconducting. From the data we find a breakdown fieldH
b
=1.2 (mG) and a coherence length =2.2T
–1/2 (m) for the Cu, as well as a field penetration depth -34T
1/2 (m) at the Cu/Nb interface. 相似文献
5.
A. A. Lipnik 《Russian Physics Journal》1989,32(6):486-489
Anisotropic acoustomagnetoelectric (AME) effects at meso-ultrasonic frequencies are calculated analytically in semiconductors with an anisotropic mobility () in arbitrary classical magnetic fields. For Bq(q is the ultrasonic wave vector) and an arbitrary direction of q two transverse components of the AME field (E
B
q E
y
B
) occur in the crystal, and the longitudinal acoustoelectric field changes under the action of a longitudinal magnetic field (E
q
B
=E
q
B
-E
q
0
),E
B
is even, and E
B
is odd in B; for B 1 the component E
y
B
E
B
/B, andE
B
and E
q
B
are independent of B and can be commensurate with the zero-field acoustoelectric field E
q
0
if the anisotropy of is large (hexagonal ZnS and ZnO or n-Ge highly compressed along [111]). The transverse AME field E
st
B
is calculated in the configuration E
st
B
qBE
st
B
(standard AMEeffect). For B >> 1 the field B 1E
st
B
B
–3, so thatE
B
, E
y
B
, and
q
B
can be greater than E
st
B
here. The acoustoelectric analog of the Grabner effect (E
G
B
), i.e., the component of the AME field along a transverse magnetic field (E
G
B
Bq) is also calculated. For pB > 1 the componentE
G
B
B
–3.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 93–97, June, 1989. 相似文献
6.
We study a new Monte Carlo algorithm for generating self-avoiding walks with variable length (controlled by a fugacity) and fixed endpoints. The algorithm is a hybrid of local (BFACF) and nonlocal (cut-and-paste) moves. We find that the critical slowing-down, measured in units of computer time, is reduced compared to the pure BFACF algorithm:
CPU
N2.3 versus N3.0. We also prove some rigorous bounds on the autocorrelation time for these and related Monte Carlo algorithms. 相似文献
7.
Radu Miron 《International Journal of Theoretical Physics》2000,39(9):2327-2336
A suitable dual for the k-acceleration bundle(T
k
M,
k
,M) is the fiberedbundle (T
k–1
M×
M
T*M). The mentioned bundle carries a canonicalpresymplectic structure and k canonical Poisson structures. By means of thisdual we define the notion of Hamilton spaces of orderk, whose total spaceconsists of points x of the configuration spaceM, accelerations of order 1,...,k – 1, y
(1),...,y
(k–1), and momenta p. Some remarkable Hamiltonian systemsare pointed out. There exists a Legendre mapping from the Lagrange spaces oforder k to the Hamilton space of order k. 相似文献
8.
We study the ground state properties of theS=1/2 Heisenberg antiferromagnet (HAF) on the triangular lattice with nearest-neighbour (J) and next-nearest neighbour (J) couplings. Classically, this system is known to be ordered in a 120° Néel type state for values-<1/8 of the ratio of these couplings and in a collinear state for 1/8<<1. The order parameter and the helicity /gC of the 120° structure are obtained by numerical diagonalisation of finite periodic systems of up toN=30 sites and by applying the spin-wave (SW) approximation to the same finite systems. We find a surprisingly good agreement between the exact and the SW results in the entire region-<<1/8. It appears that the SW theory is still valid for the simple triangular HAF (=0) although the sublattice magnetisation is substantially reduced from its classical value by quantum fluctuations. Our numerical results for the order parameterM of the collinear order support the previous conjecture of a first order transition between the 120° and the collinear order at 1/8. 相似文献
9.
We study a two-layer neural network made of N and M(N) neurons, producing a two-way association search for a family of p(N) patterns, where each pattern is a pair of two independent sub-categories of information having respectively N and M(N) components. In terms of the ratio =lim
N
M(N)/N, we study the retrieval capability of this network and show that there exists, at least, three regimes of association for which we determine the evolution of the threshold
c
() of the storage capacity =lim
N
p(N)/N. 相似文献
10.
Miklós Rédei 《Foundations of Physics》1995,25(3):411-422
The projection latticesP(1),P(2) of two von Neumann subalgebras 1, 2 of the von Neumann algebra are defined to be logically independent if A B0 for any 0AP(1), 0BP(2). After motivating this notion in independence, it is shown thatP(1),P(2) are logically independent if 1 is a subfactor in a finite factor andP(1),P(2 commute. Also, logical independence is related to the statistical independence conditions called C*-independence W*-independence, and strict locality. Logical independence ofP(1,P(2 turns out to be equivalent to the C*-independence of (1,2) for mutually commuting 1,2 and it is shown that if (1,2) is a pair of (not necessarily commuting) von Neumann subalgebras, thenP(1,P(2 are logically independent in the following cases: is a finite-dimensional full-matrix algebra and 1,2 are C*-independent; (1,2) is a W*-independent pair; 1,2 have the property of strict locality. 相似文献
11.
Y. Zhou J. Zhou X. Chang F. Xia C. H. Shih 《Applied Physics A: Materials Science & Processing》1996,62(3):213-216
The microstructure of fiber-like SiC/Si3N4 composite particulate was investigated using high-resolution transmission electron microscopy techniques. The SiC/Si3N4 composite particulate consisted of a-SiC core and a -Si3N4 outer shell. Two kinds of composite particulate were distinguished when the observed orientation of the SiC core was <110>. In one type of the SiC/Si3N4 composite particulate, a crystal relationship of (111)-SiC | (102) -Si3N4 and (111)-SiC (114) -Si3N4 was identified; in the other type of the SiC/Si3N4 composite particulate, a crystal relationship of (111)-SiC (001) -Si3N4, and (111)-SiC (101) -Si3N4 was observed. 相似文献
12.
We examine the steady-state flux of particles diffusing in a one-dimensional finite chain with Sinai-type disorder, i.e., the system in which in addition to the thermal noise, particles are subject to a stationary random-correlated in space Gaussian force. For this model we calculate the disorder average (over configurations of the random force) flux exactly for arbitrary values of system's parameters, such as chain lengthN, strength of the force, and temperature. We prove that within the limitN1 the average flux decreases withN as J(N)=C/N and thus confirm our recent predictions that the flux in the discrete-space Sinai model is anomalous. 相似文献
13.
G. Bollen 《Hyperfine Interactions》1993,78(1-4):57-66
Nuclear physics experiments with ion traps started at the on-line separator ISOLDE/CERN, Geneva, with the installation of the tandem Penning trap mass spectrometer ISOLTRAP. With this device the massM of a stored ion is determined by measuring its cyclotron frequency c=(q/M)B in a magnetic fieldB. Mass measurements with a resolving powerR=c/c(FWHM)1×106 and accuracies of M/M10–7 were performed on more than sixty unstable isotopes of the elements Rb, Sr, Cs, Ba, Fr, and Ra. 相似文献
14.
Barnsley M. F. Geronimo J. S. Harrington A. N. 《Communications in Mathematical Physics》1983,88(4):479-501
The Julia setB
for the mappingz (z–)2 is considered, where is a complex parameter. For 2 a new upper bound for the Hausdorff dimension is given, and the monic polynomials orthogonal with respect to the equilibrium measure onB
are introduced. A method for calculating all of the polynomials is provided, and certain identities which obtain among coefficients of the three-term recurrence relations are given. A unifying theme is the relationship betweenB
and -chains ± (± (± ...), which is explored for –1/42 and for with ||1/4, with the aid of the Böttcher equation. ThenB
is shown to be a Hölder continuous curve for ||<1/4.Supported by NSF Grant MCS-8104862Supported by NSF Grant MCS-8002731 相似文献
15.
We prove exponential convergence to equilibrium (L
2 geometric ergodicity) for a random walk with inward drift on a sub-Cayley rooted tree. This randomwalk model generalizes a Monte Carlo algorithm for the self-avoiding walk proposed by Berretti and Sokal. If the number of vertices of levelN in the tree grows asC
N
~
N
N
–1
, we prove that the autocorrelation time satisfies N2 N1+ 相似文献
16.
C. M. Newman 《Journal of statistical physics》1986,45(3-4):359-368
For a large class of independent (site or bond, short- or long-range) percolation models, we show the following: (1) If the percolation densityP
(p) is discontinuous atp
c
, then the critical exponent (defined by the divergence of expected cluster size, nP
n
(p) (P
c
–P)– asp p
c
) must satisfy 2. (2) or (defined analogously to, but asp p
c
) and [P
n
(p
c
) (n
–1–1/) asn ] must satisfy, 2(1 – 1/). These inequalities for improve the previously known bound 1(Aizenman and Newman), since 2 (Aizenman and Barsky). Additionally, result 1may be useful, in standardd-dimensional percolation, for proving rigorously (ind>2) that, as expected,P
x
has no discontinuity atp
c
. 相似文献
17.
R. L. Ingraham 《Zeitschrift für Physik B Condensed Matter》1992,87(1):83-87
The thermodynamics (including energy gap and critical temperatureT
c
) of a two-dimensional type II BCS superconductor subjected to a strong transverse magnetic fieldH in the re-entrant regime is studied. There are qualitative differences with the re-entrant 3D case; in particularT
c
grows unboundedly likeB/lnB asB (filling factor 1) for fixedN. The thermodynamics atT=0 is completely described by the evaluation of the magnetic Gibbs free energy as a function of andH. A first order magnetic phase transition (failure of H/ B>0 for around each lowlying Landau level) found for the normal phase for unbroadened Landau levels, is washed out in the superconducting phase. 相似文献
18.
We investigate the influence of long range interactions on the relaxation behaviour of a lattice model with an on-site potential of
4-type and infinite range harmonic interactions. For finite number of particlesN, it is shown that the autocorrelation functions <E
n(t)E
n
> of the fluctuations of the one-particle energiesE
n(t) decays exponentially. The corresponding relaxation time is proportional toN and is given by (T, N) =N0(T). The temperature dependent time scale 0 can explicitly be related to the dynamics of a one-particle correlator of the noninteracting system. The results are derived using Mori-Zwanzig projection formalism. The corresponding memory kernel is calculated within a mode coupling approximation and by a perturbative approach. Both results agree in leading order in 1/N. It is speculated that any interaction of range generates a timescale . 相似文献
19.
Marek Czachor 《Foundations of Physics Letters》1992,5(3):249-264
We discuss two classical situations that lead to probabilities characteristic for systems with spin-1/2. (a) Pitowsky model: It is demonstrated that the definition of spin functions does not imply which circle (a parallel or a great circle) on the sphere should be taken as a probability space in calculation of conditional probabilities. Pitowsky's choice of parallels must be formulated as an assumption about the model. It is shown that the model explicitly avoiding this difficulty is possible and no contradiction with the Bell Theorem is found. The modification is based on a new pathological decomposition of the sphere and belongs to a class of hidden variable theories with undetected signals. (b) Aerts model: We show the importance of the polarization effect of the measurements for the sake of obtaining a non-Kolmogorovian probability model. It is also shown that the conditioning by a change of state leads in general to the non-Kolmogorovian probability calculus.2. For example, let Cw,z xCw,zµc ({y C
w,z S
+|(x,y) /2})=µ
c(C
w,z S
+)= 1/2µ
c(C
w,z). Pitowsky spheres with white points distributed onC
w,z in this way exist. The proof is exactly analogous to this of Theorem 1 in [1]. Then (**) = 1 -/, if one takesC
w,z as the probability space. This example seems very instructive.3. If the chargeq falls down on some point then it clearly has not fallen down on another one. Having given a result of a measurement we cannot, within the model with polarization, talk in a sensible way about its alternative: We can think either aboutsuccessive measurements (then the Bell inequality is not derivable) or ask What would have happened if..., but then we deal with a different problem (in Aerts' terminology [2b] this is anobservation) and obtain again Eq. (8) (there is no complementarity but there is no model of spin either). 相似文献
20.
L. G. Kharitonov 《Russian Physics Journal》1966,9(5):76-78
An equation is derived for the hyperbola which touches the true stress curve S =f(), where is the contraction of the specimen at the point p (uniform contraction), SB (true ultimate strength). With a flat maximum of the tensile force, this hyperbola coincides with the true stress curve at a part corresponding to extension by the maximum force. The use of the tangent hyperbola for determining p and SB is demonstrated.It is found that for those metals and alloys which are at present known to have a convex true stress curve in the uniform plasticity range, the uniform contraction p cannot exceed 0.5, corresponding to a uniform elongation p 1, while the true (logarithmic) uniform elongation p 0.693. The limiting values of the hardening modulus and of the ratio SB/B are also found. 相似文献