共查询到20条相似文献,搜索用时 62 毫秒
1.
Exciting a hexagonal CdSe crystal with picosecond Nd: glass laser pulses, two-photon absorption and resonant non-phase-matched second-harmonic generation occur simultaneously. Using different crystal orientations, all components of the secondharmonic susceptibility tensor (non-vanishing components ared
31,d
33 andd
15) and some components of the two-photon absorption susceptibility tensor
ijkl
(3)
(–L; L, L, –L) are determined. 相似文献
2.
The mean square tilt angle of a nematic slab with finite anchoring energy and periodic boundary conditions has been theoretically investigated, as a function of the slab geometry and of the reduced extrapolation length. If the anchoring strength is free-surfacelike, the contrast is affected by a loss 10% at room temperature if the ratio between the anchoring pitch and the cell thickness is 0.5.Glossary
anchoring pitch
-
h
cell thickness
-
/h
- ( = x/, = y/h)
reduced coordinates
-
(, )
local tilt angle
-
elastic constant
- wa
anchoring energy anisotropy
-
b=/w
a
de Gennes-Kleman extrapolation length
-
B=b/h
reduced extrapolation length
-
T
NI
nematic-isotropic transition temperature
-
:=(T/T
NI
) – 1
reduced temperature
-
easy axis direction
-
MAX
-
±
2
mean square tilt angle along the boundary
-
()
absorbance coefficients of the p-dye
-
r
/: dichroic ratio
-
c
contrast
-
G
contrast gain
-
S
order parameter 相似文献
3.
A relation between a.c. spectrum of ergodic Jacobi matrices and the spectra of periodic approximants
Y. Last 《Communications in Mathematical Physics》1993,151(1):183-192
We study ergodic Jacobi matrices onl
2(Z), and prove a general theorem relating their a.c. spectrum to the spectra of periodic Jacobi matrices, that are obtained by cutting finite pieces from the ergodic potential and then repeating them. We apply this theorem to the almost Mathieu operator: (H
, ,
u)(n)=u(n+1)+u(n–1)+ cos(2n+)u(n), and prove the existence of a.c. spectrum for sufficiently small , all irrational 's, and a.e. . Moreover, for 0<2 and (Lebesgue) a.e. pair , , we prove the explicit equality of measures: |ac|=||=4 –2.Work partially supported by the US-Israel BSF 相似文献
4.
Successive band-splitting transitions occur in the one-dimensional map xi+1=g(xi),i=0, 1, 2,... withg(x)=x, (0 x 1/2) –x +, (1/2 <x 1) as the parameter is changed from 2 to 1. The transition point fromN (=2n) bands to 2Nbands is given by=(2)1/N (n=0, 1,2,...). The time-correlation function
i=xix0/(x0)2,xi xi–xi is studied in terms of the eigenvalues and eigenfunctions of the Frobenius-Perron operator of the map. It is shown that, near the transition point=2,
i–[(10–42)/17] i,0-[(102-8)/51]i,1 + [(7 + 42)/17](–1)ie–yi, where2(–2) is the damping constant and vanishes at=2, representing the critical slowing-down. This critical phenomenon is in strong contrast to the topologically invariant quantities, such as the Lyapunov exponent, which do not exhibit any anomaly at=2. The asymptotic expression for
i has been obtained by deriving an analytic form of
i for a sequence of which accumulates to 2 from the above. Near the transition point=(2)1/N, the damping constant of
i fori N is given by
N=2(N-2)/N. Numerical calculation is also carried out for arbitrary a and is shown to be consistent with the analytic results. 相似文献
5.
Alan D. Sokal 《Journal of statistical physics》1981,25(1):25-50
A variety of rigorous inequalities for critical exponents is proved. Most notable is the low-temperature Josephson inequalitydv +2 2–. Others are 1 1 +v, 1 1
, 1,d 1 + 1/ (for d),dv, 3 + (for d), 4 , and 2m 2m+2 (form 2). The hypotheses vary; all inequalities are true for the spin-1/2 Ising model with nearest-neighbor ferromagnetic pair interactions.NSF Predoctoral Fellow (1976–1979). Research supported in part by NSF Grant PHY 78-23952. 相似文献
6.
V. I. Mel'nikov 《Journal of statistical physics》1993,70(1-2):77-91
We consider the effect of a high-frequency pumping cost on the escape rate of a classical underdamped Brownian particle out of a deep potential well. The energy dependence of the oscillation frequency(E) is assumed to be weak on the scale of thermal energy,E(0)T(0)T/V0 (0)[E(0) is the derivative of(E) atE= 0,V
0 is the barrier height,V
0 T]. The quadratic-in- contribution to the decay rate is calculated in two different regimes: (1) for the case of resonance of the pumping frequency with the nth harmonic of the internal motion at an energye, when
= n(e); (2) for a rollout region of the basic resonance near the bottom of the potential well, when ¦-(0)¦ and is the damping coefficient. In the latter case the absorption spectrum and the enhancement of the decay rate are calculated as functions of two reduced parameters, the anharmonicity of the potential,v
E
(0)T/, and the resonance mismatch, [ —(0)]/. It is shown that the effect of the pumping increases with diminishing ¦v¦ and at small v is proportional tov
–1. In this regime, the dependence on is stepwise: the pumping contribution is large for v > 0 and small for v < 0. In the frame of our theory, the decay rate is invariant against the simultaneous alternation of the signs of andv. The spectrum of the energy absorption has the standard Lorentzian shape in the absence of anharmonicity,v=0, and with increasing of ¦v¦ shifts and widens retaining its bell-shape form. 相似文献
7.
George Svetlichny 《Foundations of Physics》1986,16(12):1285-1295
LetA be a quasi-manual with finite operations. Associate to each E = {e
1
,..., en} A the set E of modal formulas: (e
1
··· en), ei (e
1
··· ei–1
ei+1
··· en), i=1,..., n. Set
A
= {E|E A}. We show that supports ofA are in one-to-one correspondence with certain Kripke models of
A
where the supports are given by {x |A x is true}.On leave from the Department of Mathematics, Pontificia Universidade Catolica, Rio de Janeiro, Brazil. 相似文献
8.
The paper gives the results of measuring the temperature dependence of the electrical conductivity(T), the Hall coefficientR
H
(T) and the magnetic susceptibility(T) forn-type CdSnAs2. The effective mass of the electrons was determined by analysis of the measured dependences on the basis of the simple theory for an isotropic non-degenerate semi-conductor. It was found to bem
n
/m
0=2×10–2 in the intrinsic region and does not depend on the temperature; the energy gap ise
g
0=0·26 eV and the molar susceptibility of the CdSnAs2 lattice
G
mol=–112× ×10–6. The mobility of the electrons in the intrinsic region reaches a value of
n
=25 000 cm2V–1sec–1 at 500°K and decreases exponentially
n
T
–1.67 with rising temperature. The density of CdSnAs2 was determined pyknometrically,g9=5·35 g cm–3. The measurements were made on ann-type polycrystalline sample consisting of crystals a few millimetres in diameter, which at a temperature of 100°K had a free electron concentration ofn
s
=6×1016 cm–3.
The authors would like to thank Mr. P. Jansa for help in measuring the temperature dependence of the magnetic susceptibility. 相似文献
CdSnAs2
(T), R H (T) (T) CdSnAs2 . m n /m 0= =2.10–2, ; E G 0=0,26 eV, CdSnAs2 G mol= =–112.10–6. 500°K n =25 000 cm2V–1sec–1 , n T –1,67. CdSnAs2 =5,35 g cm–3. , , 100°K n s =6.1016cm–3.
The authors would like to thank Mr. P. Jansa for help in measuring the temperature dependence of the magnetic susceptibility. 相似文献
9.
M. Ghosh A. K. Sen B. K. Chakrabarti G. A. Kohring 《Journal of statistical physics》1990,61(1-2):501-504
The variation of the convergence time, as a function of the storage capacity is studied numerically for systems ranging in size fromN=1000 toN=16,000 neurons. is found to increase likeexp[–A(c–)] as one nears the critical storage capacity
c
=0.142=0.002. 相似文献
10.
E. Hiyama 《Few-Body Systems》2004,34(1-3):79-84
From the viewpoint of critical stability, we discuss the three- and four-body structure of 6He, 7He, 4He, and 4H. With the + + N three-body model, 6He is found to have a three-layer structure of the matter distribution: core, a skin and neutron halo. Also the level structure of 7He with the three-body model of 5He + n + n is predicted. This stimulates a new study of neutron-rich and proton-rich hypernuclei. By performing a four-body calculation with both NNN and NNN channels and with both NN and NNN channels, we show that the N-N and -N couplings are very important in critical stability of few-body hypernuclear systems. 相似文献
11.
Juraj Dubinský Pavel Chaloupka Václav Petržílka Lenka Tomášková 《Czechoslovak Journal of Physics》1956,6(1):29-33
( - .). , - , - , - . , D=30 40% , ; D=50 60%. . 相似文献
12.
We study spectral properties of the discrete Laplacian H on the half space Z+
d+1 = Zd× Z+ with a boundary condition (n,-1) = tan( ... n + )(n,0), where [0,1]d. We denote by H0 the Dirichlet Laplacian on Z+
d+1. Whenever is independent over rationals (H) = R. Khoruzenko and Pastur have shown for a set of 's of Lebesgue measure 1, the spectrum of H on R\ (H0) is pure point and that corresponding eigenfunctions decay exponentially. In this Letter we show that if is independent over rationals, then the spectrum of H on the set (H0) is purely absolutely continuous. 相似文献
13.
Ola Bratteli Richard H. Herman Derek W. Robinson 《Communications in Mathematical Physics》1978,59(2):167-196
For automorphism groups of operator algebras we show how properties of the difference
t
– '
t
are reflected in relations between the generators , . Indeed for a von Neumann algebraM with separable predual we show that if t – 't 0.28 for smallt, then = 0(+)°-1 where is an inner automorphism ofM and is a bounded derivation ofM. If the difference
t
– '
t
=O(t) ast ; 0, then = + and if
t
– '
t
0.28 for allt then =. We prove analogous results for unitary groups on a Hilbert space andC
0,C
0
*
groups on a Banach space.This paper subsumes an earlier work of the same title which appeared as a report from Z.I.F. der Universität BielefeldWith partial support of the U.S. National Science Foundation 相似文献
14.
Benjamin Enriquez 《Letters in Mathematical Physics》1994,31(1):15-33
We define deformations of the Poisson bracket algebras of functions on manifolds
= {
+
i
/
=1w
i
-i
|w
i
C
(S
1)} of pseudodifferential symbols on the circle ( C), arising in the works of Rosly and Khesin-Zakharevich. These deformations have vertex operator algebraic (VOA) counterparts, which have (for =n integer) a quotient isomorphic to theW-algebraW
n
associated by Fateev and Lukyanov to gl
n
.The product operation of symbols defines a Lie-Poisson structure on
C
L
(Rosly, Khesin-Zakharevich); we show that this structure has also a VOA counterpart. 相似文献
15.
Granville A. Perkins 《Foundations of Physics》1978,8(3-4):177-189
A null 4-vector °, based on Dirac's relativistic electron equation, is shown explicitly for a plane wave and various Coulomb states. This 4-vector constitutes a mechanical model for the electron in those states, and expresses the important spinor quantities represented conventionally byn, f, g, m, j, ,1, ands. The model for a plane wave agrees precisely with the relation between velocity and phase gradient customarily used in quantum theory, but the models for Coulomb states contradict that relation. 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.
Rinaldo Schinazi 《Journal of statistical physics》1994,74(5-6):1005-1016
The contact process onZ has one phase transition; let
c
be the critical value at which the transition occurs. Let
N
be the extinction time of the contact process on {0,...,N}. Durrett and Liu (1988), Durrett and Schonmann (1988), and Durrett, Schonmann, and Tanaka (1989) have respectively proved that the subcritical, supercritical, and critical phases can be characterized using a large finite system (instead ofZ) in the following way. There are constants 1() and 2() such that if <
c
, lim
N
N
/logN = 1/1(); if >
c
, lim
N
log
N
/N = 2(); if =
c
, lim
N
N
/N= and lim
N
N
/N
4=0 in probability. In this paper we consider the asymmetric contact process onZ when it has two distinct critical values
c1<
c2. The arguments of Durrett and Liu and of Durrett and Schonmann hold for <
c1 and >
c2. We show that for [
c1<
c2), lim
N
N
/N=-1/, (where
i
is an edge speed) and for =
c2, lim
N
log
N
/logN=2 in probability. 相似文献
18.
O. A. Fonarev 《Russian Physics Journal》1990,33(9):759-764
We define a covariant and gauge-invariant generalization of the Wigner functions of particles with spins 1/2 and 0. The collisionless kinetic equations are obtained for these particles in external gravitational and electromagnetic fields in the quasiclassical approximation; also obtained are the momentum representations of the energy-momentum tensor, current, and spin tensor, taking into account the effects of the spin's interaction with the gravitational field an electromagnetic field. The following notation is used: e and m are the charge and mass of the particles; is Planck's constant; (x) are the covariant-fixed Dirac matrices; ,=(1/4)[, ]: a(b)=(1/2) (a
b
+ab
); [A, B]=A·B – B·A; A,B=A·B+B·A; g(x)=det(g
(x));R
=
–...; the speed of light c=1.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 47–53, September, 1990.The author wishes the thank Yu. G. Ignat'ev and members of the seminar in General Relativistic Statistics and Cosmology of the Kazan' Pedagogical Institute for useful discussions. 相似文献
19.
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
20.
Z. Haba 《Letters in Mathematical Physics》1996,37(2):223-231
Let
t
be an analytic solution of the Schrödinger equation with the initial condition . Let
t
be the solution of the Schrödinger equation with the initial condition =, where is an analytic function. When 0, then
t
(x)
t
(x)1 (
t
(x)), where
t
(x) trajectory starting from x. We relate this result to Feynman's sum over trajectories and complex stochastic differential equations. 相似文献