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1.
C. Chris Wu 《Journal of statistical physics》1996,88(5-6):1399-1408
We consider an inhomogeneous contact process on a tree
of degreek, where the infection rate at any site isλ, the death rate at any site in
isδ (with 0 <δ ⩽ 1) and that at any site in
is 1. Denote by
the critical value for thehomogeneous model (i.e.,δ=1) on
and byϑ(δ, λ) the survival probability of the inhomogeneous model on
. We prove that whenk > 4, if
, a subtree embedded in
, with 1 ⩽σ ⩽ √k, then three existsδ
c
σ
strictly between (
) and 1 such that (
) whenδ >δ
c
σ
andϑ(δ, λ
c(
) > 0 whenδ <δ
c
σ
; ifS={o}, the origin of
, then
for anyδ ε (0, 1). 相似文献
2.
We study analogues of the Yangian of the Lie algebra
for the other classical Lie algebras
and
. We call them twisted Yangians. They are coideal subalgebras in the Yangian of
and admit homomorphisms onto the universal enveloping algebras U(
) and U(
) respectively. In every twisted Yangian we construct a family of maximal commutative subalgebras parametrized by the regular semisimple elements of the corresponding classical Lie algebra. The images in U(
) and U(
) of these subalgebras are also maximal commutative. 相似文献
3.
Explicit evaluation of the following parameters has been carried out in the extraU (1) superstring inspired model: (i) As Mz2 varies from 555 GeV to 620 GeV and (m
t) CDF = 175.6 ± 5.7 GeV (Table 1): (a) SNew varies from -0.100 ± 0.089 to -0.130 ± 0.090, (b) TNew varies from -0.098 ± 0.097 to -0.129 ± 0.098, (c) UNew varies from -0.229 ± 0.177 to -0.253 ± 0.206, (d) Τz varies from 2.487 ± 0.027 to 2.486 ± 0.027, (e) ALR varies from 0.0125 ± 0.0003 to 0.0126 ± 0.0003, (f) A
FB
b
remains constant at 0.0080 ± 0.0007. Almost identical values are obtained for (m
t)D0 = 169 GeV (see table 2). (ii) Triple gauge boson vertices (TGV) contributions: AsMz
2 varies from 555 GeV to 620 GeV and (m
t) CDF = 175.6 ±5.7 GeV. (a)√s = 500 GeV, asymptotic case:
varies from -0.301 to -0.179;
varies from -0.622 to -0.379;
varies from +0.0061 to 0.0056;
varies from -3.691 to -2.186.
varies from +0.270 to +0.118;
varies from +0.552 to 0.238;
varies from +0.0004 to +0.0002;
remains constant at -0.110. (b)√s = 700 GeV, asymptotic case:
varies from -0.297 to -0.176;
varies from -0.609 to -0.370;
varies from -0.0082 to -0.0078;
varies from -3.680 to -2.171.√s = 700 GeV, nonasymptotic case:
varies from -0.173 to -0.299;
varies from-0.343 to -0.591;
varies from -0.005 to -0.011;
remains constant at -0.110.
The pattern of form factors values for√s = 1000, 1200 GeV is almost identical to that of√s= 700 GeV. Further the values of the form factors for (m
t)D0 (=169 GeV) follow identical pattern as that of (m
t) CDF form factors values (see tables 5, 6, 9, 10).
We conclude that the values of all the form factors with the exception of these of
,
are comparable or larger than theS, T values and therefore the TGV contributions are important while deciding the use of extraU (1) model for doing physics beyond standard model. 相似文献
4.
The existence of a topological double-covering for the GL(n, R) and diffeomorphism groups is reviewed. These groups do not
have finite-dimensional faithful representations. An explicit construction and the classification of all
(n, R), n=3,4 unitary irreducible representations is presented. Infinite-component spinorial and tensorial
fields, “manifields”, are introduced. Particle content of the ladder manifields, as given by the
(3, R) “little” group, is determined. The manifields are lifted to the corresponding world spinorial and tensorial manifields
by making use of generalized infinite-component frame fields. World manifields transform w.r.t. corresponding
representations, which are constructed explicitly.
Supported in part by the Science Foundation (Belgrade). 相似文献
5.
We consider the problem of generation of small-scale quasistatic electric fields that can lead to establishment of the bipolar
regime of inhomogeneity relaxation observed in experimental studies of the properties of an artificial turbulence excited
in the upper ionosphere by high-power shortwave radio emission [1–8], which is slower than the regime of unipolar diffusion
of quasineutral fluctuations of density in a homogeneous strongly magnetized plasma [9–11]. We show that necessary conditions
for the existence of this mode are disruption of the symmetry of the initial disturbance in the plasma density with respect
to the direction of the field
and its differential rotation with the drift frequency in the plane orthogonal to
. Assuming that the initial disturbance of the plasma has the form of a plane wave whose wave vector
makes an angle
with the normal to
, we obtain an expression for the drift frequency and study the relations between the fluctuational electric and magnetic
fields and the drift velocity of the disturbed plasma in, the linear approximation. We discuss the properties of the nonlinear
solution, which, in particular, can describe generation of small-scale plasma inhomogeneities that have a helical structure
in the plane orthogonal to
. The phenomenon of frequency broadening of the Doppler spectra of signals of field-aligned SW and USW scattering observed
in the case of field-aligned scattering of short and ultrashort radio waves by artificial ionospheric inhomogeneities [4–7]
is interpreted.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 41, No. 2, pp. 194–211, February, 1998. 相似文献
6.
José M. Figueroa-O'Farrill 《Communications in Mathematical Physics》1996,177(1):129-156
Let
be a finite-dimensional Lie algebra (not necessarily semisimple). It is known that if
is self-dual (that is, if it possesses an invariant metric) then it admits anN=1 (affine) Sugawara construction. Under certain additional hypotheses, thisN=1 structure admits anN=2 extension. If this is the case,
is said to possess anN=2 structure. It is also known that anN=2 structure on a self-dual Lie algebra
is equivalent to a vector space decomposition
, where
are isotropic Lie subalgebras. In other words,N=2 structures on
in one-to-one correspondence with Manin triples
. In this paper we exploit this correspondence to obtain a classification of thec=9N=2 structures on solvable Lie algebras. In the process we also give some simple proofs for a variety of Lie algebras. In the process we also give some simple proofs for a variety of Lie algebraic results concerning self-dual Lie algebras admitting symplectic or Kähler structures. 相似文献
7.
Summary Grain growth is studied in polycrystalline ice, consisting of elongated grains, of (200÷300) μm mean width
and (2÷3) mm mean length
. The samples are annealed at different temperatures, between 0°C and −10°C. It is found that
is not affected by annealing, while
increases with the annealing time. Below the melting point,
(t) tends to a limit value
. This behaviour is related to the pinning action of air bubbles, which would be similar to that found for solid inclusions
in metals. By assuming
where
is the mean bubble diameter andf is the volume fraction of air dissolved in water, reasonable values are found for
. The activation energy of the phenomenon is evaluated on the basis of the present and of Jellinek and Gouda's results. It
is foundQ=0.6 eV, which value approximately coincides with that for bulk self-diffusion as it occurs for metals, several degrees below
the melting point. This coincidence suggests that, for ice, grain growth would be controlled by bulk impurity diffusion up
to the very melting point.
Instituto de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and CONICET. 相似文献
8.
Ruedi Suter 《Communications in Mathematical Physics》1994,163(2):359-393
The restricted quantum universal enveloping algebra
decomposes in a canonical way into a direct sum of indecomposable left (or right) ideals. They are useful for determining the direct summands which occur in the tensor product of two simple
. The indecomposable finite-dimensional
are classified and located in the Auslander-Reiten quiver. 相似文献
9.
The product of two real spectral triples
and
, the first of which is necessarily even, was defined by A.Connes as
given by
and, in the even-even case, by
. Generically it is assumed that the real structure
obeys the relations
,
,
, where the
-sign table depends on the dimension n modulo 8 of the spectral triple. If both spectral triples obey Connes'
>-sign table, it is seen that their product, defined in the straightforward way above, does not necessarily obey this
-sign table. In this Letter, we propose an alternative definition of the product real structure such that the
-sign table is also satisfied by the product. 相似文献
10.
11.
Let
be the Haag--Kastler net generated by the
(2) chiral current algebra at level 1. We classify the SL(2,
)-covariant subsystems
by showing that they are all fixed points nets
H
for some subgroup H of the gauge automorphisms group SO(3) of
. Then, using the fact that the net
1 generated by the
(1) chiral current can be regarded as a subsystem of
, we classify the subsystems of
1. In this case, there are two distinct proper subsystems: the one generated by the energy-momentum tensor and the gauge invariant subsystem
. 相似文献
12.
Giving an ultraviolet regularization and volume cut off we construct a nuclear Riemannian structure on the Hilbert manifold
of gauge orbits. This permits us to define a regularized Laplace-Beltrami operator on
and an associated global diffusion in
governed by . This enables us to define, via a Feynman-Kac integral, a Euclidean, continuum regularized Yang-Mills process corresponding to a suitable regularization (of the kinetic term) of the classical Yang-Mills Lagrangian onT
.On leave of absence from Zaragoza University (Spain)Laboratoire associé au CNRS 相似文献
13.
Stefano De Leo Zbigniew Oziewicz Waldyr A. Rodrigues Jayme Vaz 《International Journal of Theoretical Physics》1999,38(9):2349-2369
We formulate the variational principle of theDirac equation within the noncommutative even space-timesubalgebra, the Clifford
-algebra
. A fundamental ingredient in ourmultivectorial algebraic formulation is a
-complex geometry,
. We derive the Lagrangian for theDirac-Hestenes equation and show that it must be mapped on
, where denotes an
-algebra of functions. 相似文献
14.
Garry Ludwig 《General Relativity and Gravitation》1983,15(11):1085-1097
In a recent paper it was shown how to construct, under certain circumstances, asymptotic (Newman-Unti) series expansions for
the spin-coefficient variables for real space-times from data obtained from a given left-flat space in an appropriate frame.
If these expansions represent asymptotically flat space-times the latter have the given left-flat space as their H space.
The method was described in a frame in which the asymptotic left-shear
was zero whereas
was not. For the discussion of algebraically special left-flat spaces it is more convenient to have
vanish and
remain nonzero. In this paper we determine all algebraically special left-flat spaces with diverging rays, utilizing Penrose's
conformal technique, and then show in detail how to find the “initial data” for the construction of asymptotic series expansions
for the corresponding real space-times. 相似文献
15.
Sergio Doplicher Daniel Kastler Derek W. Robinson 《Communications in Mathematical Physics》1966,3(1):1-28
Starting from aC*-algebra
and a locally compact groupT of automorphisms of
we construct a covariance algebra
with the property that the corresponding *-representations are in one-to-one correspondence with covariant representations of
i.e. *-representations of
in which the automorphisms are continuously unitarily implemented. We further construct for relativistic field theory an algebra
yielding the *-representations of
in which the space time translations have their spectrum contained inV. The problem of denumerable occurence of superselection sectors is formulated as a condition on the spectrum of
. Finally we consider the covariance algebra
built with space translations alone and show its relevance for the discussion of equilibrium states in statistical mechanics, namely we restore in this framework the equivalence of uniqueness of the vacuum, irreducibility and a weak clustering property.On leave of absence from Istituto di Fisica G. Marconi — Roma. 相似文献
16.
B. I. Deutch 《Hyperfine Interactions》1992,73(1-2):175-191
The main suggested routes for atomic antihydrogen (
) formation will be reviewed in a pedestrian fashion. These are the following reactions:
, and (iii)
. The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be
discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe. 相似文献
17.
We consider the decomposition of the conformal blocks under the conformal embeddings. The case
(â is an affine extension of the abelian subalgebra of the central elements ofgl(lr)) is studied in detal. The reciprocal decompositions of
-modules induce a pairing between the spaces of conformal blocks of
and
Wess-Zumino-Witten models on the Riemann sphere. The completeness of the pairing is shown. Hence it defines aduality between two spaces.Dedicated to Professor Masahisa Adachi on his 60th birthday 相似文献
18.
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
19.
We report results on event-by-event fluctuations in mean transverse momentum in AuAu collisions at
GeV measured by the STAR experiment at RHIC. The dynamical fluctuations,
is found to be about 1.2 ±02% of the mean transverse momentum for particles in pseudo-rapidity range of −0.5 < η < 0.5 and
for the top 6% central collisions. 相似文献
20.
S. L. Woronowicz 《Communications in Mathematical Physics》1972,28(3):221-235
Let
be aC*-algebra and
be an opposite algebra. Notions of exact andj-positive states of
are introduced. It is shown, that any factor state of
can be extended to a pure exactj-positive state
of
. The correspondence
generalizes the notion of the purifications map introduced by Powers and Størmer. The factor states 1 and 2 are quasi-equivalent if and only if their purifications
and
are equivalent. 相似文献