共查询到20条相似文献,搜索用时 52 毫秒
1.
A. Duda 《Acoustical Physics》2006,52(1):36-42
I reanalyze the problem of the existence of longitudinal normals inside the symmetry planes of piezoelectric crystals belonging
to the symmetry class mm2. The equations determining components of longitudinal normals situated outside the symmetry planes for media of this symmetry
are discussed. It is proven that nonpiezoelectric media of rhombic symmetry could have 4 or 8 distinct acoustic axes. Examples
of nonpiezoelectric elastic media of monoclinic symmetry without acoustic axes are given. The method of determination of the
components of acoustic axes for piezoelectric media of arbitrary symmetry is presented. With the help of this method, I discuss
the problem of acoustic axes for piezoelectric media of the symmetry class mm2.
The text was submitted by the author in English. 相似文献
2.
In this paper, the Lie symmetry algebra of the coupled
Kadomtsev--Petviashvili (cKP) equation is obtained by the classical Lie group method and
this algebra is shown to have
a Kac--Moody--Virasoro loop algebra structure. Then the general symmetry groups of the cKP
equation is also obtained by the symmetry group direct method which is proposed by Lou et al。 From the
general symmetry groups, the Lie symmetry group can be recovered and a group
of discrete transformations can be derived simultaneously. Lastly,
from a known simple solution of the cKP equation, we can easily obtain
two new solutions by the general symmetry groups. 相似文献
3.
Lu-Xin Liu 《Physics of Atomic Nuclei》2011,74(12):1684-1689
In this paper a Weyl scale-invariant p = 3-brane scenario is introduced, with the brane embedded in a higher-dimensional bulk space with N = 1, 5D Super-Weyl symmetry. Its action, which describes its long wave oscillation modes into the ambient superspace and
breaks the target symmetry down to the lower dimensional Weyl W(1, 3) symmetry, is constructed by the approach of coset method. 相似文献
4.
S. E. Burkov 《Journal of statistical physics》1988,52(1-2):453-461
Hamiltonians for nonperiodic tilings are considered. It is shown that the quasicrystalline tiling obtained by the cut-and-strip method from aD-dimensional cubic lattice may bs a ground state only if the tiling possesses a high orientational symmetry: the (2,D)-quasicrystal should haveD-fold symmetry ifD is even and 2D-fold symmetry ifD is odd. For interactions of a finite range the restrictions are stronger: only a (2, 5)-quasicrystal (Penrose tiling) may be a stable ground state. 相似文献
5.
A.D. Bandrauk 《Molecular physics》2013,111(3):661-664
The V symmetry coupling coefficients for the icosahedral double group are generated from the behaviour of a minimum number of |JM> ket vectors where the symmetry coupling coefficients are defined as analogues of the Racah V coefficients. The phases are determined from the way the irreducible representations for the specific J values are defined. An investigation of the symmetry properties of the system by a translation of the |JM> ket vectors for integral J values is examined. The handling of the irreducible-tensor method in group notation is discussed briefly. 相似文献
6.
Salvatore Capozziello Noemi Frusciante Daniele Vernieri 《General Relativity and Gravitation》2012,44(8):1881-1891
Spherical symmetry for f (R)-gravity is discussed by searching for Noether symmetries. The method consists in selecting conserved quantities in form
of currents that reduce dynamics of f (R)-models compatible with symmetries. In this way we get a general method to obtain constants of motion without setting a priori the form of f (R). In this sense, the Noether symmetry results a physical criterium. Relevant cases are discussed. 相似文献
7.
D. Lee 《The European Physical Journal A - Hadrons and Nuclei》2008,35(2):171-187
The symmetric heavy-light ansatz is a method for finding the ground state of any dilute unpolarized system of attractive two-component
fermions. Operationally it can be viewed as a generalization of the Kohn-Sham equations in density functional theory applied
to N -body density correlations. While the original Hamiltonian has an exact Z2 symmetry, the heavy-light ansatz breaks this symmetry by skewing the mass ratio of the two components. In the limit where
one component is infinitely heavy, the many-body problem can be solved in terms of single-particle orbitals. The original
Z2 symmetry is recovered by enforcing Z2 symmetry as a constraint on N -body density correlations for the two components. For the 1D, 2D, and 3D attractive Hubbard models the method is in very
good agreement with exact Lanczos calculations for few-body systems at arbitrary coupling. For the 3D attractive Hubbard model
there is very good agreement with lattice Monte Carlo results for many-body systems in the limit of infinite scattering length. 相似文献
8.
The role of lower symmetry component of the crystal field in causing a mixing of excited 3d
x−1 4s with the ground 3d
x
configuration and leading to spin density at the nucleus for iron group ions was suggested by Griffith and Orgel. This mechanism
has been examined in detail for the two low-symmetry copper complexes, one square planar (D4h symmetry) and the other distorted tetrahedron (D2d symmetry) and the calculation has been performed using the powerful Racah method and tensor operator technique. It is found
that for the two types of copper complexes, copper pthalocyanin (square planar, D4h symmetry) and cesium copper chloride (distorted tetrahedron, D2d symmetry) the contribution from this mechanism to the spin density at the nucleus vanishes identically. 相似文献
9.
10.
R. Gonczarek L. Jacak M. Krzyzosiak A. Gonczarek 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(2):171-186
Based upon the tight-binding formalism a model of a
high-Tc superconductor with isotropic and anisotropic
attractive interactions is considered analytically. Symmetry
facets of the group C4v are included within a method of
successive transformations of the reciprocal space. Complete sets
of basis functions of C4v irreducible representations are
given. Plausible spin-singlet and spin-triplet superconducting
states are classified with regard to the chosen basis functions. It
is displayed that pairing interaction coefficients and the
dispersion relation, which can be characterized by the parameter
η= 2t1/t0, have a diverse and mutually competing
influence on the value of the transition temperature. It is also
shown that
in the case of a nearly half-filled conduction band
and an anisotropic pairing interaction the spin-singlet
d-wave symmetry superconducting state is realized for
small values of the parameter η, whereas in the opposite
limit, for sufficiently large values, the spin-triplet
p-wave symmetry superconducting state has to be formed.
This result cannot be obtained within the Van Hove scenario or
BCS-type approaches, where the p-wave symmetry
superconducting state absolutely dominates. The specific heat jump
and the isotope shift as functions of the parameter η are
assessed and discussed for the d-wave symmetry singlet and
the p-wave symmetry triplet states. 相似文献
11.
The symmetry classification of possible singlet and also triplet states in the case of the 2-dim square lattice, and 3-dim tetragonal and orthorhombic lattices is examined. If particle-hole symmetry is present then an additional symmetry classification is possible. However in the lower symmetry crystal structures that actually occur, no distinction on symmetry grounds can be drawn between usuals-wave, extendeds-wave and some of thed-wave states. 相似文献
12.
13.
Satoshi Watamura 《General Relativity and Gravitation》2011,43(9):2479-2490
We discuss the Hopf algebra structure in string theory and present the twist quantization as a unified formulation of the
world sheet quantization of the string and the symmetry of the target spacetime. Applying it to the case with a nonzero B-field background, we explain a method to decompose the twist into two successive twists. There are two different possibilities
of decomposition: The first is a natural decomposition from the viewpoint of the twist quantization, leading to a new type
of twisted Poincaré symmetry. The second decomposition reveals the relation of our formulation to the twisted Poincaré symmetry
on the Moyal type noncommutative space. 相似文献
14.
Sameer M. Ikhdair 《Central European Journal of Physics》2012,10(2):361-381
Using an approximation scheme to deal with the centrifugal (pseudo-centrifugal) term, we solve the Dirac equation with the
screened Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number κ. Based on the spin and pseudospin symmetry, analytic bound state energy spectrum formulas and their corresponding upper-
and lower-spinor components of two Dirac particles are obtained using a shortcut of the Nikiforov-Uvarov method. We find a
wide range of permissible values for the spin symmetry constant C
s
from the valence energy spectrum of particle and also for pseudospin symmetry constant C
ps
from the hole energy spectrum of antiparticle. Further, we show that the present potential interaction becomes less (more)
attractive for a long (short) range screening parameter α. To remove the degeneracies in energy levels we consider the spin and pseudospin solution of Dirac equation for Yukawa potential
plus a centrifugal-like term. A few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa, the Yukawa plus
centrifugal-like potentials, the limit when α becomes zero (Coulomb potential field) and the non-relativistic limit of our solution are studied. The nonrelativistic solutions
are compared with those obtained by other methods. 相似文献
15.
C. -S. Jia P. Guo Y. -F. Diao L. -Z. Yi X. -J. Xie 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):41-48
By using the basic concepts of the supersymmetric quantum mechanics formalism and the function analysis method, we solve the
Dirac equation with vector and scalar potentials and obtain the bound-state solutions for the nuclei in the relativistic P?schl-Teller
potential. All of the analyses are prepared under the conditions of the exact spin symmetry and pseudospin symmetry. The exact
energy equation and corresponding two-component spinor wave functions for s -wave bound states are obtained analytically. 相似文献
16.
In this work the analysis of the equivalent rotations from the permutation inversion group formalism is revisited. We emphasize that explicit knowledge of changes in the Euler angles are not required in order to determine the transformation that a given symmetry operation causes to the rotational functions when dealing with the permutation inversion group formalism. Indeed, matrix elements of the equivalent rotations are provided by a single Wigner's D (j)(R) function. Taking advantage of this, we propose a symmetry projection approach to build the rovibrational functions of methane. This approach focuses on the relevance of the isomorphism between permutations and equivalent rotations. In our method, symmetry adapted functions are obtained by simultaneous diagonalization of a set of commuting operators, whose representation is given in terms of direct products of Wigner's D functions and vibrational matrix representations provided by a local scheme. The proposed approach is general and permits us to obtain in a systematic fashion an orthonormal set of symmetry-projected functions, with good total angular momentum, and carrying the irreducible representations of the molecular symmetry group. 相似文献
17.
The systematic discussion of the elastic and structural properties of the tetragonal paramagnetic model with the maximum value of the total angular momentumJ=1 in an external magnetic field along thez orx direction is given. The sound velocities of all the symmetry modes are calculated by using the standard perturbation theory and Green's function method. It is shown that only in the presence of the external field directed along thez-axis, for some values of this field and temperature one of the symmetry elastic constantsc
44 orc
B becomes zero and the phase transition to monoclinic (triclinic) or volume change transition can occur. 相似文献
18.
Takeshi Araki Ryo Takahashi 《The European Physical Journal C - Particles and Fields》2009,63(4):521-526
We investigate the Friedberg–Lee (FL) symmetry and its promotion to include the μ–τ symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward
the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation
of the FL symmetry. The second one is based on the S
3 permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each
scheme are also presented. 相似文献
19.
The static properties of the sphericalp-spin interaction spin glass model are calculated using the replica method. It is shown that within the Parisi scheme the most general solution is the one-step replica symmetry breaking. The transition from the replica symmetric solution to the replica replica symmetry broken one is either continuous or discontinuous inq
1–q0 depending on the strength of the external magnetic field. The model can be solved explicitly for anyp at any temperature and magnetic field. Below the transition we find an infinite number of metastable states. 相似文献
20.
M.B. Sheftel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):203-206
Using the heavenly equation as an example, we propose the method of group foliation as a tool for obtaining non-invariant
solutions of PDEs with infinite-dimensional symmetry groups. The method involves the study of compatibility of the given equations
with a differential constraint, which is automorphic under a specific symmetry subgroup and therefore selects exactly one
orbit of solutions. By studying the integrability conditions of this automorphic system, i.e. the resolving equations, one can provide an explicit foliation of the entire solution manifold into separate orbits. The
new important feature of the method is the extensive use of the operators of invariant differentiation for the derivation
of the resolving equations and for obtaining their particular solutions. Applying this method we obtain exact analytical solutions
of the heavenly equation, non-invariant under any subgroup of the symmetry group of the equation.
Received 13 September 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: sheftel@gursey.gov.tr 相似文献