共查询到20条相似文献,搜索用时 31 毫秒
1.
B. Ya. Balagurov 《Journal of Experimental and Theoretical Physics》2011,112(2):327-332
The conductivity of a weakly inhomogeneous anisotropic medium is considered. The effective conductivity tensor $
\hat \sigma _e
$
\hat \sigma _e
is determined in the approximation quadratic in deviation of local conductivity $
\hat \sigma
$
\hat \sigma
(r) from mean value 〈$
\hat \sigma
$
\hat \sigma
〉 for an arbitrary anisotropy of the composite. 相似文献
2.
Measuring the $
\bar \nu _e
$
\bar \nu _e
component of the cosmic diffuse supernova neutrino background (DSNB) is the next ambitious goal for low-energy neutrino astronomy.
The largest flux is expected in the lowest accessible energy bin. However, for E ≲ 15 MeV a possible signal can be mimicked by a solar $
\bar \nu _e
$
\bar \nu _e
flux that originates from the usual 8B neutrinos by spin-flavor oscillations. We show that such an interpretation is possible within the allowed range of neutrino
electromagnetic transition moments and solar turbulent field strengths and distributions. Therefore, an unambiguous detection
of the DSNB requires a significant number of events at E ≳ 15 MeV. 相似文献
3.
We present a scheme for the evaluation of the conductivity and other effective properties of a model composite with a regular anisotropic structure, namely, a 2D system with circular inclusions forming a rectangular array. Exact expressions for the electric potential and the effective conductivity tensor [^(s)] e\hat \sigma _e were obtained in the form of infinite series. For small inclusion densities, a virial expansion for [^(s)] e\hat \sigma _e was derived from the general formulas and its applicability conditions were found. The first terms of this expansion yield the well-known Rayleigh result for the isotropic model (square array). 相似文献
4.
Spin correlations for the ΛΛ and Λ$
\bar \Lambda
$
\bar \Lambda
pairs, generated in relativistic heavy-ion collisions, and related angular correlations at the joint registration of hadronic
decays of two hyperons, in which space parity is not conserved, are analyzed. The correlation tensor components can be derived
from the double angular distribution of products of two decays by the method of “moments”. The properties of the “trace” of
the correlation tensor (a sum of three diagonal components), determining the relative fractions of the triplet states and
singlet state of respective pairs, are discussed. Spin correlations for two identical particles (ΛΛ) and two nonidentical
particles (Λ$
\bar \Lambda
$
\bar \Lambda
) are considered from the viewpoint of the conventional model of one-particle sources. In the framework of this model, correlations
vanish at sufficiently large relative momenta. However, under these conditions, in the case of two nonidentical particles
(Λ$
\bar \Lambda
$
\bar \Lambda
) a noticeable role is played by two-particle annihilation (two-quark, two-gluon) sources, which lead to the difference of
the correlation tensor from zero. In particular, such a situation may arise when the system passes through the “mixed phase.” 相似文献
5.
B. Ya. Balagurov 《Technical Physics》2013,58(8):1164-1172
The electrical conductivity of a structurally anisotropic two-dimensional model for a composite material is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of mutually perpendicular scratches of various lengths. The centers of the scratches are chaotically distributed in plane (x, y). The approximate effective medium method is used to derive an expression for effective conductivity tensor $\hat \sigma _e$ that satisfactorily describes the electrical conductivity of this model over a wide concentration range. The model conductivity in the critical region is considered in terms of the similarity hypothesis. 相似文献
6.
V. P. Ruban 《Journal of Experimental and Theoretical Physics》2010,111(5):776-785
We consider slow, compared to the speed of sound, motions of an ideal compressible fluid (gas) in a gravitational field in
the presence of two isentropic layers with a small specific-entropy difference between them. Assuming the flow to be potential
in each of the layers (v
1, 2 = ▿ϕ1, 2) and neglecting the acoustic degrees of freedom (div($
\bar \rho
$
\bar \rho
(z)▿ϕ1, 2) ≈ 0, where $
\bar \rho
$
\bar \rho
(z) is the average equilibrium density), we derive the equations of motion for the boundary in terms of the shape of the surface
z = η(x, y, t) itself and the difference between the boundary values of the two velocity field potentials: ψ(x, y, t) = ψ1 − ψ2. We prove the Hamilto nian structure of the derived equations specified by a Lagrangian of the form ℒ = ∫$
\bar \rho
$
\bar \rho
(η)η
t
ψdxdy − ℋ{η, ψ}. The system under consideration is the simplest theoretical model for studying internal waves in a sharply stratified
atmosphere in which the decrease in equilibrium gas density due to gas compressibility with increasing height is essentially
taken into account. For plane flows, we make a generalization to the case where each of the layers has its own constant potential
vorticity. We investigate a system with a model dependence $
\bar \rho
$
\bar \rho
(z) ∝ e
−2αz
with which the Hamiltonian ℋ{η, ψ} can be represented explicitly. We consider a long-wavelength dynamic regime with dispersion
corrections and derive an approximate nonlinear equation of the form u
t
+ auu
x
− b[−$
\hat \partial _x^2
$
\hat \partial _x^2
+ α2]1/2
u
x
= 0 (Smith’s equation) for the slow evolution of a traveling wave. 相似文献
7.
Yu. I. Romanov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):492-495
Electroweak (EW) and electromagnetic (EM) scattering of solar beryllium neutrinos by electrons are analyzed. An analysis of the influence of the mean-square charge
radius of an electron neutrino $
r_{\nu _e } = \sqrt {\left\langle {r_{_{\nu _e } }^2 } \right\rangle }
$
r_{\nu _e } = \sqrt {\left\langle {r_{_{\nu _e } }^2 } \right\rangle }
on differential and total cross sections is performed. The possibility of measuring the magnetic moment of an electron neutrino
(μv) on the basis of isolating its contribution to the section of the discussed processes is considered. 相似文献
8.
E. A. Kataeva A. D. Bozhko S. V. Demishev 《Bulletin of the Lebedev Physics Institute》2010,37(11):347-351
The conductivity of carbon films grown by polymethylphenylsiloxane vapor decomposition in stimulated dc discharge plasma was
studied. It is found that the Mott hopping conductivity $
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
$
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
is characteristic of the samples under study in the temperature range of 80–400 K in the electric field E to 5 · 104 V/cm. An analysis of the pre-exponential factor σ
0(T) = σ
00(T
0)T
α allowed the conclusion that the hopping transport is most adequately described in the model with the exponential energy dependence
of the density of localized states for which α = −1/2 and the universal relation ln σ
00 −T
01/4 0 is valid, which is satisfied in the range where the parameter σ
00 varies by eight orders of magnitude. 相似文献
9.
G. H. Arakelyan A. B. Kaidalov C. Merino Yu. M. Shabelski 《Physics of Atomic Nuclei》2011,74(3):426-436
The WA89 Collaboration experimental data on production of Λ, Σ−, Σ+, Ξ−, Ω− baryons, $
\bar \Lambda
$
\bar \Lambda
and $
\bar \Xi ^ +
$
\bar \Xi ^ +
antibaryons in Σ− collisions with C and Cu targets at 345 GeV/c ($
\sqrt {s_{\Sigma N} }
$
\sqrt {s_{\Sigma N} }
≈ 25.5 GeV) in the frame of the Quark-Gluon String Model is described. The comparison of the theoretical results with the
experimental data is discussed. Finally, some relations among the values of the model parameters obtained with the help of
quark combinatorics are presented. 相似文献
10.
We calculate the asymmetries in parity-nonconserving deuteron photodisintegration due to circularly polarized photons $
\vec \gamma d \to np
$
\vec \gamma d \to np
with the photon laboratory energy ranging from the threshold up to 10MeV and the radiative capture of thermal polarized neutrons
by protons $
\vec np \to \gamma d
$
\vec np \to \gamma d
. We use the leading-order electromagnetic Hamiltonian neglecting the smaller nuclear exchange currents. Comparative calculations
are done by using the Reid93 and Argonne v18 potentials for the strong interaction and the DDH and FCDH “best” values for the weak couplings in a weak one-meson exchange
potential. A weak NΔ transition potential is used to incorporate also the Δ(1232) -isobar excitation in the coupled-channels formalism. 相似文献
11.
Yu. S. Surovtsev T. Branz T. Gutsche V. E. Lyubovitskij 《Physics of Particles and Nuclei》2010,41(6):990-993
In a model-independent approach the data on ππ → ππ, K
$
\bar K
$
\bar K
, ηη, ηη′ in the I
G
J
PC
= 0+0++ channel and on the Kπ scattering in the $
I\left( {J^P } \right) = \frac{1}
{2}\left( {0^ + } \right)
$
I\left( {J^P } \right) = \frac{1}
{2}\left( {0^ + } \right)
channel are analyzed jointly for studying the status and QCD nature of the f
0- and the K*0-mesons. It is shown that in the 1500-MeV region, there are two states, wide (interpreted as a glueball) and narrow (q
$
\bar q
$
\bar q
). In the Kπ-scattering data analysis, the proof for the K*0(900) is given. 相似文献
12.
Utilizing the Baym-Kadanoff formalism with the polarization function calculated in the random phase approximation, the dynamics
of the ν = 0 quantum Hall state in bilayer graphene is analyzed. Two phases with nonzero energy gap, the ferromagnetic and
layer asymmetric ones, are found. The phase diagram in the plane ($
\bar \Delta _0
$
\bar \Delta _0
, B), where $
\bar \Delta _0
$
\bar \Delta _0
is a top-bottom gates voltage imbalance, is described. It is shown that the energy gap scales linearly, ΔE ∼ 14B [T] K, with magnetic field. 相似文献
13.
The cascade mass reconstruction approach was used for mass reconstruction of the lightest $
\tilde \tau
$
\tilde \tau
produced at the LHC in the cascade decay $
\tilde g \to \tilde bb \to \tilde \chi _2^0 bb \to \tilde \tau _1 \tau bb \to \tilde \chi _1^0 \tau \tau bb
$
\tilde g \to \tilde bb \to \tilde \chi _2^0 bb \to \tilde \tau _1 \tau bb \to \tilde \chi _1^0 \tau \tau bb
. The $
\tilde \tau _1
$
\tilde \tau _1
mass was reconstructed assuming that masses of gluino, bottom squark, and two lightest neutralinos were reconstructed in
advance. SUSY data sample sets for the SU(3) model point containing 160k events each were generated which corresponded to an integrated luminosity of about 8 fb−1 at 14 TeV. These events were passed through the AcerDET detector simulator, which parametrized the response of a generic
LHC detector. The mass of the $
\tilde \tau _1
$
\tilde \tau _1
was reconstructed with a precision of about 20% on average. 相似文献
14.
M. N. Zakharenkov 《Thermophysics and Aeromechanics》2009,16(3):391-396
The known problem of flow transition near a circular cylinder at Re = 40 from a symmetrical form to the Karman vortex street
can be considered as the problem of vortex wave development and intensification. Development of three bundles of vortex waves
of low intensity is observed in a wake of a cylinder; these bundles are easily visualized as the structures of relative vorticity
$
\bar \Omega
$
\bar \Omega
= Ω(t
1) − Ω(t
0): difference of vorticity Ω at two time moments, t
0 being fixed. In the field of $
\bar \Omega
$
\bar \Omega
the alternating structure of quadrupoles is characterized by linear parameter l = h/d: the ratio of the width of the central bundle of vortex waves to the distance between the centers of quadrupoles of a “single
sign”. When l = 0.281 is achieved, which coincides with the value of the same parameter of a stable Karman street, the transition from
symmetrical streamlining by viscous incompressible liquid to the vortex street occurs. 相似文献
15.
The Blume-Emery-Griffiths model with the dipole-quadrupole interaction ($
\ell = \frac{I}
{J}
$
\ell = \frac{I}
{J}
) has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton (CCA) on the face centered
cubic (fcc) lattice. The finite-size scaling relations and the power laws of the order parameter (M) and the susceptibility (χ) are proposed for the dipole-quadrupole interaction (ℓ). The dipole-quadrupole critical exponent
δχ has been estimated from the data of the order parameter (M) and the susceptibility (χ). The simulations have been done in the interval $
0 \leqslant \ell = \frac{I}
{J}0 \leqslant 0.01
$
0 \leqslant \ell = \frac{I}
{J}0 \leqslant 0.01
for $
d = \frac{D}
{J} = 0,k = \frac{K}
{J} = 0
$
d = \frac{D}
{J} = 0,k = \frac{K}
{J} = 0
and $
h = \frac{H}
{J} = 0
$
h = \frac{H}
{J} = 0
parameter values on a face centered cubic (fcc) lattice with periodic boundary conditions. The results indicate that the
effect of the ℓ parameter is similar to the external magnetic field (h). The critical exponent δℓ are in good agreement with the universal value (δ
h
= 5) of the external magnetic field. 相似文献
16.
B. Ya. Balagurov 《Journal of Experimental and Theoretical Physics》2014,118(2):311-322
The conductivity of composites in the presence of a magnetic field H is considered. The galvanomagnetic characteristics for a weakly inhomogeneous medium are determined in explicit form in an approximation quadratic in the deviations of conductivity tensor $\hat \sigma $ (r) from its mean value 〈 $\hat \sigma $ 〉. The contribution to the effective conductivity tensor $\hat \sigma _e $ linear in concentration c of inclusions for a composite with a small value of c is expressed in terms of the dipole polarizability of an individual inclusion, which is defined in the transformed system in which it is surrounded by an isotropic matrix with a scalar conductivity. Transition to this system is performed using a symmetry transformation that does not change the dc equations. An approximate approach proposed for describing the galvanomagnetic properties of composites in the wide range of parameters appearing in the problem generalizes the standard theory of an effective medium to the case of anisotropic systems with inclusions of arbitrary shape in field H ≠ 0. 相似文献
17.
The results of the calculation of electron bands of bound states that cross the edge of the continuous spectrum for the (001)
fcc copper monolayer are presented for the first time. The calculations are performed in the local approximation for the exchange
and correlations using the film variant of the Green’s function technique. Symmetry of electron states near the edge of the
continuous spectrum is explored. It is found that there are bound states along the $
\bar \sum
$
\bar \sum
direction of the two-dimensional Brillouin zone of the Cu(001) monolayer that are embedded in the continuum of delocalized
states of the continuous spectrum. Along the $
\bar \Delta
$
\bar \Delta
and $
\bar Y
$
\bar Y
directions, bands of bound states turn into resonance states after crossing the edge of the continuous spectrum. 相似文献
18.
B. Ya. Balagurov 《Journal of Experimental and Theoretical Physics》2011,113(5):849-856
A general approach is proposed for calculating the conductivity of anisotropic composites with a low concentration of inclusions
of an arbitrary shape. The contribution to effective conductivity [^(s)] e\hat \sigma _e, which is linear in concentration, is expressed in terms of the polarizability of the inclusion defined in a certain transformed
system in which the inclusion is surrounded by an isotropic matrix. A transition to this system is performed using a symmetry
transformation that does not change the equations for direct current. 相似文献
19.
The thermodynamic properties of a cluster of point Coulomb charges on a sphere have been analyzed using the Monte Carlo method
for the number of charges 20 ≤ N ≤ 90. The ground state of the system of charges is described in the model of a closed quasi-two-dimensional triangular lattice
with topological defects. We have determined the dependence of the Lindeman parameter δL of this system on N and on the dimensionless parameter $
\tilde T
$
\tilde T
, which is proportional to the temperature T and to the radius R of the cluster: $
\tilde T = {{k_B T\varepsilon R} \mathord{\left/
{\vphantom {{k_B T\varepsilon R} {e^2 }}} \right.
\kern-\nulldelimiterspace} {e^2 }}
$
\tilde T = {{k_B T\varepsilon R} \mathord{\left/
{\vphantom {{k_B T\varepsilon R} {e^2 }}} \right.
\kern-\nulldelimiterspace} {e^2 }}
, where ∈ is the dielectric constant of the medium and e is the charge of a particle. The “magic numbers,” i.e., the N values, for which the melting point of the closed triangular lattice of charges is much higher than those for neighboring
N values, have been found. The evolution of the lattice-melting mechanisms with an increase in the number of charges N in a mesoscopic cluster has been analyzed. For N ≤ 32, the melting of the lattice does not involve dislocations (nontopological melting); this behavior of the mesoscopic
system of charges on the sphere differs from the behavior of the extended planar two-dimensional system. At N ≳ 50, melting is accompanied by the formation of dislocations. The mechanism of dislocation-free non-topological melting
of a closed lattice, which occurs at small N values and is associated with the cooperative rotational motion of “rings” of particles, has been analyzed. The model has
various implementations in the mesoscopic region; in particular, it describes the system of electrons over the liquid-helium
cluster, the liquid-helium cluster with incorporated charged particles, a multielectron bubble in liquid helium, a charged
quantum dot, etc. 相似文献
20.
A. V. Anisovich V. V. Anisovich M. A. Matveev V. A. Nikonov J. Nyiri A. V. Sarantsev 《Physics of Atomic Nuclei》2010,73(7):1254-1265
We consider as an example the two-pion decay of the ρ meson, the 3
S
1
q
$
\bar q
$
\bar q
state of the constituent quarks—the decay being determined by the transition q
$
\bar q
$
\bar q
→ ππ contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung
radiation of a pion q → q + π (or $
\bar q
$
\bar q
→ $
\bar q
$
\bar q
+ π) with a subsequent fusion q
$
\bar q
$
\bar q
→ π, and (ii) the direct transition q
$
\bar q
$
\bar q
→ ππ. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what
is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions
of processes with bremsstrahlung radiation of the pion and of the direct transition q
$
\bar q
$
\bar q
→ ππ. The estimates demonstrate that the processes involving the direct transition q
$
\bar q
$
\bar q
→ ππ are necessary, but they cannot be determined unambiguously by the decay ρ(775) → ππ. We conclude that for the determination of the q
$
\bar q
$
\bar q
→ ππ transition more complete data on the resonance decays into the ππ channels are needed than those available at the moment. 相似文献