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1.
P. C. Hemmer 《Journal of statistical physics》2000,100(1-2):3-11
A binary mixture of long rigid rods of diameters D
i and lengths L
i (i=1, 2) may demix into two isotropic phases, and we give necessary conditions on the molecular size parameters for this transition to exist. These conditions imply that the two diameters must be sufficiently unequal, D
2/D
1>(
+
)2, or D
2/D
1<(
+
)2, while the length ratio is limited to an interval f
–(D
2/D
1)<L
2/L
1<f
+(D
2/D
1). The functions f
± are given explicitly. 相似文献
2.
Calculations of the two-atom surface recombination rate for spinpolarized atomic hydrogen are carried out. Both the plane-wave Born approximation (PWBA) and the
-dimensional distorted-wave model are employed. The field dependence forB=4 to 10 Tesla, and the temperature dependence for 0.2<T<1 K are examined for systems initially consisting of equal numbers ofa- andb-state atoms. The rates are analyzed with respect to para- and ortho-H2 production, and to recombination to various vibrational and rotational states of H2. The PWBA gives reasonable agreement with experiment with respect to the field-dependence and ortho-para production, but predicts an overall rate a factor of 40 above experiment. The
-dimensional model underestimates the rate by a factor of 103 and yields poorer agreement with experiment than the PWBA for the field-dependence and ortho-para production ratio. These results point out the need for a proper many-body treatment. 相似文献
3.
We study the question of existence and uniqueness of non-ideal gas in
d
with multi-body interactions among its particles. For each k-tuple of the gas particles, 2km
0<, their interaction is represented by a potential function
k
of a finite range. We introduce a stabilizing potential function
, such that (x
1,...,
) grows sufficiently fast, when diam{x
1,...,
} shrinks to 0. Our results hold under the assumption that at least one of the potential functions is stabilizing, which causes a sufficiently strong repulsive force. We prove that (i) for any temperature there exists at least one Gibbs field, and (ii) there exists exactly one Gibbs field at sufficiently high temperature, such that for any >0,
C(V
0)< for all volumes V smaller than a certain fixed finite volume V
0. The proofs use the criterion of the uniqueness of Gibbs field in non-compact case developed in ref. 4, and the technique employed in ref. 1 for studying a gas with pair interaction. 相似文献
4.
If
(V) is a net of local von Neumann algebras satisfying standard axioms of algebraic relativistic quantum field theory and V
1
and V
2
are spacelike separated spacetime regions, then the system (
(V
1
),
(V
2
), ) is said to satisfy the Weak Reichenbach's Common Cause Principle iff for every pair of projections A
(V
1
), B
(V
2
) correlated in the normal state there exists a projection C belonging to a von Neumann algebra associated with a spacetime region V contained in the union of the backward light cones of V
1
and V
2
and disjoint from both V
1
and V
2
, a projection having the properties of a Reichenbachian common cause of the correlation between A and B. It is shown that if the net has the local primitive causality property then every local system (
(V
1
),
(V
2
), ) with a locally normal and locally faithful state and suitable bounded V
1
and V
2
satisfies the Weak Reichenbach's Common Cause Principle. 相似文献
5.
A natural supersymmetric extension
is defined of the current (= affine Kac-Moody Lie) algebra
; it corresponds to a superconformal and chiral invariant 2-dimensional quantum field theory (QFT), and hence appears as an ingredient in superstring models. All unitary irreducible positive energy representations of
are constructed. They extend to unitary representations of the semidirect sumS
(G) of
with the superconformal algebra of Neveu-Schwarz, for
, or of Ramond, for =0.On leave of absence from the Institute for Nuclear Research and Nuclear Energy of the Bulgarian Academy of Sciences, BG-1184 Sofia, Bulgaria 相似文献
6.
Karl Kraus 《Communications in Mathematical Physics》1967,7(2):99-111
Concrete C*-algebras, interpreted physically as algebras of observables, are defined for quantum mechanics and local quantum field theory.Aquantum mechanical system is characterized formally by a continuous unitary representation up to a factorU
g
of a symmetry group
in Hilbert space and a von Neumann algebra on invariant with respect toU
g
. The set
of all operatorsX such thatU
g
X U
g
–1
, as a function ofg
, is continuous with respect to the uniform operator topology, is aC*-algebra called thealgebra of observables. The algebra is shown to be the weak (or strong) closure of
.Infield theory, a unitary representation up to a factorU(a, ) of the proper inhomogeneous Lorentz group
and local von Neumann algebras C for finite open space-time regionsC are assumed, with the usual transformation properties of
underU(a, ). The collection of allXC giving uniformly continuous functionsU (a, )X U
–1 (a, ) on
is then a localC*-algebra
, called thealgebra of local observables. The algebra
is again weakly (or strongly) dense in
c
. The norm-closed union
of the
for allC is calledalgebra of quasilocal observables (or quasilocal algebra).In either case, the group
is represented by automorphisms V
g
resp. V(a, ) — with V
g
X=U
g
X U
g
–1
— of theC*-algebra
, and this is astrongly continuous representation of
on the Banach space
. Conditions for V (a, ) can then be formulated which correspond to the usualspectrum condition forU (a, ) in field theory.Work supported in part by the Deutsche Forschungsgemeinschaft. 相似文献
7.
P. Dita 《Communications in Mathematical Physics》1994,159(3):581-591
The parametrisation of ann×n unitary matrix by the moduli of its elements is not a well posed problem, i.e. there are continuous and discrete ambiguities which naturally appear. We show that the continuous ambiguity is (n–1)(n–3)-dimensional in the general case and
in the symmetric caseS
ij=Sij. We give also lower bounds on the number of discrete ambiguities, the number of solutions being at least
in the first case and
for the symmetric one, where [r] denotes the integral part ofr. 相似文献
8.
Kiselev V. V. Likhoded A. K. Shevlyagin M. V. 《Zeitschrift fur Physik C Particles and Fields》1994,63(1):77-86
The cross-section for the production of
quarks ine
+
e
– annihilation, that proves to be at a level of
for
is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of 1S-and 2S-wave states ofB
c-meson in the reaction
were calculated in the nonrelativistic model of a heavy quarkonium. The number of
bc
-hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality. 相似文献
9.
A. E. Dorokhov N. I. Kochelev Yu. A. Zubov 《Zeitschrift fur Physik C Particles and Fields》1995,65(4):667-679
The spectrum of
, Jp=0+, 2+ mesons is discussed. We have shown that due to instanton-induced forces the physical states are strong mixtures of theSU
f
(3) group basis states. The cross-sections for annihilation of the
system into
mesons are obtained. Thea
0(980) meson is considered as
meson consisting of 9
f
and 36
f
plets. The branchings are also predicted for the cross-sections for production of thea
0(980) and tensor
mesons in
annihilation. 相似文献
10.
T. Kodaira T. Ikeda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):299-302
AgI clusters were incorporated into Li, Na, and K-form LTA
zeolites with a loading number of four AgI molecules per -cage.
The X-ray powder diffraction (XRD) patterns and optical
absorption spectra of the samples were obtained. The XRD
patterns indicate that the sizes of the clusters and their
arrangements depend on the type of alkali-cations. AgI clusters
with different sizes, i.e.,
(AgI)n and (AgI)8–n (5n7),
are arrayed alternatively in Na-form LTA conforming to the space
group of P213. AgI-loaded
Li-form LTA also conformed to the space group of
P213,
although (AgI)n clusters seem to be
distributed disorderly. On the contrary,
(AgI)4 cluster is in each cage in K-form
LTA conforming to the space group of
or
. The
optical spectra showed that Li and Na-form LTAs include
(AgI)n (5 n), and that K-form LTA includes
(AgI)4 cluster in each cage. 相似文献
11.
The relation between the set of transformations
of the quantum plane and the quantum universal enveloping algebra U
q
(u(2)) is investigated by constructing representations of the factor algebra U
q
(u(2))*
. The noncommuting coordinates of
, on which U
q
(2) * U
q
(2) acts, are realized as q-spinors with respect to each U
q
(u(2)) algebra. The representation matrices of U
q
(2) are constructed as polynomials in these spinor components. This construction allows a derivation of the commutation relations of the noncommuting coordinates of
directly from properties of U
q
(u(2)). The generalization of these results to U
q
(u(n)) and
is also discussed. 相似文献
12.
We study the behavior of three vicious random walkers which diffuse freely in one dimension witharbitrary diffusivitiesb
1
2
,b
2
2
,b
3
2
, except that their paths may not cross. The full distribution function is calculated exactly in the continuum limit; the exponent 3 governing the decay of the probability
of a simultaneousreunion of all three walkers aftern steps is found to varycontinuously according to
. This variation has consequences for various interfacial wetting transitions in (1+1) dimensions. It may also be related heuristically to the marginality of direct interface-wall interactions decaying asW
0/l
2 in the intermediate fluctuation regime of (1+1)-dimensional wetting, where exponents varying continuously withW
0 have recently been found. 相似文献
13.
We investigate modification of Kolmogorov wave turbulence in QCD calculating gluon spectra as functions of time in the presence of a low energy source which feeds in energy density in the infrared region at a time-dependent rate. Then considering the picture of saturation constraints as has been constructed in the “bottom-up” thermalization approach we revisit that picture for RHIC center-mass energy, W=130 GeV, and also extend it to LHC center-mass energy, W=5500 GeV, thus for two cases having an opportunity to calculate the equilibration time, τeq|therm, of the gluon system produced in a central heavy ion collision at mid-rapidity region. Thereby, at RHIC and LHC energies we can match the equilibration time, obtained from the late stage gluon spectrum of the modified Kolmogorov wave turbulence, onto that of the “bottom-up” thermalization and other evolutional approaches as well. In addition, from the revised “bottom-up” approach we find the gluon liberation coefficient to be on the average, ε0.81–1.06 at RHIC and ε0.50–0.56 at LHC. We also present other phenomenological estimates of τtherm which, at QCD realistic couplings, yield 0.45–0.65 fmτtherm0.97–2.72 fm at RHIC and 0.31–0.40 fmτtherm0.86–2.04 fm at LHC. We show that the second upper-bounds of τtherm in both cases are due to the late stage gluon spectrum of the original Kolmogorov wave turbulence in QCD, previously deduced with a low energy source which feeds in energy density at a constant rate. On the other hand, the lower-bounds and first upper-bounds of τtherm are due to the late stage gluon spectrum of the modified QCD wave turbulence, deduced here at the specific time-dependent rate. In the latter case, at certain conditions, taking also into account both very small and realistic couplings we give estimates: 0.65 fmτtherm1.29 fm at RHIC and 0.52 fmτtherm1.16 fm at LHC, as well as at realistic couplings we find 0.53<τtherm<0.7 fm at RHIC and 0.41<τtherm<0.65 fm at LHC. 相似文献
14.
We consider SU
q
(2) covariant
-matrices for the reducible3 1 representation. There are three solutions to the Yang-Baxter equation. They coincide with the previously known
-matrices for SO
q
(3) and SO
q
(3, 1). Also, they are the three
-matrices which can be constructed by using four different SU
q
(2) doublets. Only two of the three
-matrices allow a differential structure on the reducible four-dimensional quantum space. 相似文献
15.
Let (, d) be a first-order differential *-calculus on a *-algebra
. We say that a pair (, F) of a *-representation of
on a dense domain
of a Hilbert space and a symmetric operator F on
gives a commutator representation of if there exists a linear mapping : L(
) such that (adb) = (a)i[F, (b) ], a, b
. Among others, it is shown that each left-covariant *-calculus of a compact quantum group Hopf *-algebra
has a faithful commutator representation. For a class of bicovariant *-calculi on
, there is a commutator representation such that F is the image of a central element of the quantum tangent space. If
is the Hopf *-algebra of the compact form of one of the quantum groups SL
q
(n+1), O
q
(n), Sp
q
(2n) with real trancendental q, then this commutator representation is faithful. 相似文献
16.
Couch and Torrence suggest that the vacuum Einstein equations admit a larger class of asymptotically flat solutions than those exhibiting the peeling property. Starting with the assumption that
, (d/dr)
and (/x
A
)
, wherex
A
(A = 2, 3) are angular coordinates, they show that
, where 1 2 and 1<0;
, where 2 1 and 1< 1; and 4 and 3 peel as they would under the stronger peeling conditions. The Winicour-Tamburino energy-momentun and angular momentum integrals for these solutions, in general, diverge. In fact, since Couch and Torrence determine only the radial dependence of the solution, it is not clear that the solutions are well defined. We find that the stronger assumption
, (d/dr)
, and (/x
A
)
does result in well-defined solutions for which both the energy-momentum and angular momentum intergrals are not only finite but result in the same expressions as are obtained for peeling space-times. This assumption appears to be the minimal assumption that is necessary for investigating outgoing radiation at null infinity.In part based on a dissertation by Stephanie Novak and submitted to Syracuse University in partial fulfillment of the requirement for the Ph.D. degree. 相似文献
17.
G. Müller G. Mück M. Simon G. Winterling 《Applied Physics A: Materials Science & Processing》1982,29(2):63-68
The electrical properties ofn
+-window layers inp-i-n a-Si:H solar cells were characterised as a function ofn
+-layer thickness,
, by measuring firstly the activation energyE
a
of the dark conductivity and secondly the built-in potentialV
bi
of the cells.E
a
was found to increase with decreasing
attaining values as high as 0.8 eV for
5nm; bulk values, e.g.E
a
. 2eV in the amorphous andE
a<0.01 eV in the microcrystalline case, were only observed for
>20nm and for
>200nm, respectively. In contrast,V
bi
did not depend on
at all and was further found to be consistent with expectations based on the Fermi level positions in bulkn
+ andp
+-material. As a consequenceE
a
in very thin films can no longer be considered as a measure of (E
C
–E
F), the distance of the Fermi level from the conduction band edge. The apparent inconsistency inherent to theE
a
and theV
bi
results can be resolved by assuming that the deposition of then
+-material proceeds via the growth and coalescence of small islands. 相似文献
18.
W. Fricke 《Zeitschrift für Physik B Condensed Matter》1979,34(3):273-278
Optical absorption and Zeeman effect measurements on La(Pr)Cl3 show a zero magnetic field splitting of the degenerate Pr3+ levels
and
. The site symmetry of the Pr3+ ions is lowered fromC
3h
toC
s
. The resultant splittings of the doublet levels are:I
3
H
4:2|T
ak
|=(0.12±0.05)cm–1;a
3
P
1:2|T
al
|=(0.10±0.05)cm–1.The intensities of the optical transitions induced by the deformation decrease with increasing magnetic field. All observations are described by a first order perturbation calculation using a low symmetric part of the crystal field and Zeeman energy as simultaneous perturbations on a Pr3+ ion in a crystal field with site symmetryC
3h
.Project of the Sonderforschungsbereich Festkörperspektroskopie SFB65, Darmstadt—Frankfurt, supported by the Deutsche Forschungsgemeinschaft. 相似文献
19.
We consider the Dirichlet Laplacian for astrip in
with one straight boundary and a width
, where $f$ is a smooth function of acompact support with a length 2b. We show that in the criticalcase,
, the operator has nobound statesfor small
.On the otherhand, a weakly bound state existsprovided
. In thatcase, there are positive c
1,c
2 suchthat the corresponding eigenvalue satisfies
for all
sufficiently small. 相似文献
20.
Suppose that there is given a Wightman quantum field theory (QFT) whose Euclidean Green functions are invariant under the Euclidean conformal groupSO
e
(5,1). We show that its Hilbert space of physical states carries then a unitary representation of the universal (-sheeted) covering group* of the Minkowskian conformal group SO
e
(4, 2)2. The Wightman functions can be analytically continued to a domain of holomorphy which has as a real boundary an -sheeted covering
of Minkowski-spaceM
4. It is known that* can act on this space
and that
admits a globally*-invariant causal ordering;
is thus the natural space on which a globally*-invariant local QFT could live. We discuss some of the properties of such a theory, in particular the spectrum of the conformal HamiltonianH=1/2(P
0+K
0).As a tool we use a generalized Hille-Yosida theorem for Lie semigroups. Such a theorem is stated and proven in Appendix C. It enables us to analytically continue contractive representations of a certain maximal subsemigroup
of to unitary representations of*. 相似文献