共查询到20条相似文献,搜索用时 328 毫秒
1.
T.-J. Wang J.-C. Gao Yu. M. Andreev S. A. Bereznaya T. N. Kopylova Z. V. Korotchenko G. V. Lanskii T. D. Malinovskaya A. N. Morozov S. Yu. Sarkisov 《Russian Physics Journal》2007,50(6):560-565
The most probable parameters of the pure, doped, and mixed GaSe1−xSx (x ≤ 0.4) crystals (solid solutions) are presented together with the results of investigations of their crystal structure
and defects, optical and mechanical properties, and damage thresholds.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 35–40, June, 2007. 相似文献
2.
M. Davier S. Descotes-Genon A. Höcker B. Malaescu Z. Zhang 《The European Physical Journal C - Particles and Fields》2008,56(3):305-322
We revisit the determination of α
S
(m
τ
2) using a fit to inclusive τ hadronic spectral moments in light of (1) the recent calculation of the fourth-order perturbative coefficient K
4 in the expansion of the Adler function, (2) new precision measurements from BABAR of e+e− annihilation cross sections, which decrease the uncertainty in the separation of vector and axial-vector spectral functions,
and (3) improved results from BABAR and Belle on τ branching fractions involving kaons. We estimate that the fourth-order perturbative prediction reduces the theoretical uncertainty,
introduced by the truncation of the series, by 20% with respect to earlier determinations. We discuss to some detail the perturbative
prediction of two different methods: fixed-order perturbation theory (FOPT) and contour-improved perturbative theory (CIPT).
The corresponding theoretical uncertainties are studied at the τ and Z mass scales. The CIPT method is found to be more stable with respect to the missing higher order contributions and to renormalization
scale variations. It is also shown that FOPT suffers from convergence problems along the complex integration contour. Nonperturbative
contributions extracted from the most inclusive fit are small, in agreement with earlier determinations. Systematic effects
from quark-hadron duality violation are estimated with simple models and found to be within the quoted systematic errors.
The fit based on CIPT gives α
S
(m
τ
2)=0.344±0.005±0.007, where the first error is experimental and the second theoretical. After evolution to M
Z
we obtain α
S
(M
Z
2)=0.1212±0.0005±0.0008±0.0005, where the errors are respectively experimental, theoretical and due to the evolution. The result
is in agreement with the corresponding N3LO value derived from essentially the Z width in the global electroweak fit. The α
S
(M
Z
2) determination from τ decays is the most precise one to date. 相似文献
3.
A. Gasparyan J. Haidenbauer C. Hanhart K. Miyagawa 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):61-67
The prospects of utilizing the strangeness production reaction γd→K
+
Λn for the determination of the Λn low-energy scattering parameters are investigated. The spin observables that need to be measured in order to isolate the
Λn singlet (1
S
0) and triplet (3
S
1) states are identified. Possible kinematical regions where the extraction of the Λn scattering lengths might be feasible are discussed. 相似文献
4.
We study the ground state phase diagram of the two dimensional t — t′ — U Hubbard model concentrating on the competition between antiferro-, ferro-, and paramagnetism. It is known that unrestricted
Hartree–Fock- and quantum Monte Carlo calculations for this model predict inhomogeneous states in large regions of the parameter
space. Standard mean field theory, i.e., Hartree–Fock theory restricted to homogeneous states, fails to produce such inhomogeneous
phases. We show that a generalization of the mean field method to the grand canonical ensemble circumvents this problem and
predicts inhomogeneous states, represented by mixtures of homogeneous states, in large regions of the parameter space. We
present phase diagrams which differ considerably from previous mean field results but are consistent with, and extend, results
obtained with more sophisticated methods.
PACS: 71.10.Fd, 05.70.Fh, 75.50.Ee 相似文献
5.
S.-A. Ku C.-W. Luo H.-L. Lio K.-H. Wu J.-Y. Juang A. I. Potekaev O. P. Tolbanov S. Yu. Sarkisov Yu. М. Andreev G. V. Lanskii 《Russian Physics Journal》2008,51(10):1083-1089
Transmission spectra and phase matching conditions for second harmonic generation in GaSe1–x
S
x
(0 < x ≤ 0.4) solid solution crystals are experimentally investigated. An algorithm is suggested and dispersion equations are derived
that allow the phase matching angles describing best the available experimental data to be estimated as a function of the
mixing ratio x.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 80–85, October, 2008. 相似文献
6.
Shinya Kanemura Koichi Matsuda Toshihiko Ota Serguey Petcov Tetsuo Shindou Eiichi Takasugi Koji Tsumura 《The European Physical Journal C - Particles and Fields》2007,51(4):927-931
We study how to incorporate CP violation in the Froggatt–Nielsen (FN) mechanism. To this end, we introduce non-renormalizable interactions with a flavor
democratic structure to the fermion mass generation sector. It is found that at least two iso-singlet scalar fields with a
discrete symmetry imposed are necessary to generate CP violation due to the appearance of the relative phase between their vacuum expectation values. In the simplest model, the
ratios of quark masses and the Cabibbo–Kobayashi–Maskawa (CKM) matrix including the CP violating phase are determined by the CKM element |Vus| and the ratio of two vacuum expectation values of FN fields, R=|R|eiα (a magnitude and a phase). It is demonstrated how the angles φi (i=1,...,3) of the unitarity triangle and the CKM off-diagonal elements |Vub| and |Vcb| are predicted as a function of |Vus|, |R| and α. Although the predicted value of the CP violating phase does not agree with the experimental data within the simplest model, the basic idea of our scenario would
be promising if one wants to construct a more realistic model of flavor and CP violation.
PACS 11.30.Er; 12.60.-i 相似文献
7.
A. A. Starobinsky 《JETP Letters》2007,86(3):157-163
For higher-derivative f(R) gravity, where R is the Ricci scalar, a class of models is proposed, which produce viable cosmology different from the ACDM at recent times
and satisfy cosmological, Solar System, and laboratory tests. These models have both flat and de Sitter spacetimes as particular
solutions in the absence of matter. Thus, a cosmological constant is zero in a flat spacetime, but appears effectively in
a curved one for sufficiently large R. A “smoking gun” for these models would be a small discrepancy in the values of the slope of the primordial perturbation
power spectrum determined from galaxy surveys and CMB fluctuations. On the other hand, a new problem for dark energy models
based on f(R) gravity is pointed out, which is connected with the possible overproduction of new massive scalar particles (scalarons)
arising in this theory in the very early Universe.
The text was submitted by the author in English. 相似文献
8.
R. Escribano 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):454-457
The scalar contributions to the radiative decay φ→K
0ˉ0
γ are studied within the framework of the Linear Sigma Model (LσM). Theoretical predictions for the associated subprocesses φ→f
0
γ and φ→a
0
γ as well as the ratio φ→f
0
γ/a
0
γ are also given. 相似文献
9.
In the present paper, vacuum average energy-momentum tensors are calculated on a group manifold for a real scalar field by
the method of coadjoint representation orbits. An example is considered for the group SO(3). The energy-momentum tensor is
calculated for a conformally equivalent metric with the help of a conformal transformation.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 50–57, October, 2007. 相似文献
10.
C-field cosmological models based on Hoyle-Narlikar theory with variable gravitational constant G in the frame work of FRW (Friedmann-Robertson-Walker) space–time for positive and negative curvatures are investigated. To
get the deterministic solutions in terms of cosmic time t, we have assumed G=R
n
and discussed for n=−1, −2, R being scalar factor. In both the cases, creation field C increases with time, the gravitational constant G and matter density (ρ) decrease with time in the model (21). In the model (41) G decreases with time and matter density (ρ) is constant. The other physical aspects of the models are also discussed. 相似文献
11.
A. Yu. Loginov 《Physics of Atomic Nuclei》2011,74(5):740-754
The (1 + 1)-dimensional nonlinear O(3) σ model involving an explicitly broken symmetry is considered. Sphalerons are known to exist in this model. These sphalerons
are of a topological origin and are embedded kinks of the sine-Gordon model. In the case of a compact spatial manifold S
1, sine-Gordon multikinks exist in the model. It is shown that the model admits a nonstatic generalization of the sine-Gordon
kink/multikink, Q kink/multikink. Explicit expressions are obtained for the dependence of the Q kink energy and charge on the phase frequency of rotation. The Q kink is studied for stability, and expressions are obtained for the eigenfunctions and eigenfrequencies of the operator of
quadratic fluctuations. It is shown that the Q kink is unstable over the entire admissible frequency range ω ∈ [−1, 1]. The one-loop quantum correction to the static-kink mass is calculated, and the Q-kink zero mode is quantized. It is shown that, in a general static case, the field equations of the model are integrable
in quadratures. 相似文献
12.
Magnetoresistance is studied in a strongly correlated 2D electron system in Si in the critical regime in the close vicinity
of the 2D metal-insulator transition. Our data are self-consistently compared with solutions of two equations of the crossover
renormalization group theory, which describes temperature evolutions of the resistivity and interaction parameters for 2D
electron systems. Good agreement is found between the ρ(T, B
∥) data and the renormalization group theory in a wide range of the in-plane fields, 0–2.1 T. This agreement supports the interpretation
of the observed 2D MIT as the true quantum phase transition.
The text was submitted by the authors in English. 相似文献
13.
N. M. Agababyan V. V. Ammosov M. Atayan N. Grigoryan H. Gulkanyan A.A. Ivanilov Zh. Karamyan V. A. Korotkov 《Physics of Atomic Nuclei》2007,70(11):1904-1912
The characteristics of the charged-current neutrino—nuclear interactions are investigated for the first time at E
ν
= 1–3 GeV using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam at the Serpukhov
accelerator. The E
ν
dependence of the mean multiplicities of different types of secondary particles and their multiplicity, momentum, and angular
distributions are measured.
The text was submitted by the authors in English. 相似文献
14.
We investigate the Hawking radiation and greybody factor for a scalar field on the background of the black holes in the theory
of the non-minimal R
β
F
2-coupled electromagnetic fields to gravity. For different asymptotic structures caused by the real power number β, we find that the influences of the real power number on the Hawking radiation and greybody factor are different. We also
show that the different coupling constant also affects the Hawking radiation and greybody factor. 相似文献
15.
A. C. dos Reis 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):474-478
The issue of Kπ and ππ
S-wave amplitude is addressed using decays of D-mesons. Model-independent measurements of the phases of the π
+
π
+ and K
-
π
+
S-wave amplitude from D
+→π
-
π
+
π
+ and D
+→K
-
π
+
π
+ decays are discussed. The result indicates a deviation from the phase of the K
-
π
+
S-wave amplitude obtained by scattering experiments. This could be interpreted as an indication of the presence of 3-body final-state
interaction, or in other words, that the phases from production and scattering process cannot be directly compared. 相似文献
16.
R. Kamiński J. R. Peláez F. J. Ynduráin 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):479-484
We first review the results of an analysis of ππ interactions in S, P and D waves for the two-pion effective mass from threshold to about 1.4GeV. In particular, we show a recent improvement of this
analysis above the Kˉ threshold using more data for phase shifts and including the S0-wave inelasticity from ππ→Kˉ. In addition, we have improved the fit to the f
2(1270)-resonance and used a more flexible P-wave parametrization above the Kˉ threshold and included an estimation of the D2-wave inelasticity. The better accuracy thus achieved also required a refinement of the Regge analysis above 1.42GeV. Finally,
in this work we check that the ππ scattering amplitudes obtained in this approach satisfy remarkably well forward dispersion relations and Roy's equations. 相似文献
17.
Taeyoon Moon Yun Soo Myung Edwin J. Son 《The European Physical Journal C - Particles and Fields》2011,71(10):1777
We study the stability of the f(R)-AdS (Schwarzschild–AdS) black hole obtained from f(R) gravity. In order to resolve the difficulty of solving fourth-order linearized equations, we transform f(R) gravity into scalar–tensor theory by introducing two auxiliary scalars. In this case, the linearized curvature scalar becomes
a dynamical scalaron, showing that all linearized equations are second order. Using the positivity of gravitational potentials
and S-deformed technique allows us to guarantee the stability of f(R)-AdS black hole if the scalaron mass squared satisfies the Breitenlohner–Freedman bound. This is confirmed by computing quasinormal
frequencies of the scalaron for the f(R)-AdS black hole. 相似文献
18.
Yu. A. Simonov 《Physics of Atomic Nuclei》2007,70(1):44-52
The 3d gluodynamics which governs the large-T quark—gluon plasma is studied in the framework of the field correlator method. Field correlators and spacial string tension
are derived through the gluelump Green’s functions. The glueball spectrum is calculated both in C = −1 as well as in C = +1 sectors, and multigluon bound states in the form of “gluon rings” and “gluon stars” are computed explicitly. Good overall
agreement with available lattice data is observed.
The text was submitted by the author in English. 相似文献
19.
Piotr T. Chruściel Justin Corvino James Isenberg 《Communications in Mathematical Physics》2011,304(3):637-647
Given a collection of N solutions of the (3 + 1) Einstein constraint equations which are asymptotically Euclidean and vacuum near infinity, we show
how to construct a new solution of the constraints which is itself asymptotically Euclidean, and which contains specified
sub-regions of each of the N given solutions. This generalizes earlier work which handled the time-symmetric case, thus providing a construction of large
classes of initial data for the many body problem in general relativity. 相似文献