共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
We present in this paper the results of our calculation of five-fold differential cross-section (FDCS) for (e,3e) process on He atom in low momentum transfer and high electron impact energy in shake-off mechanism. The formalism has been
developed in Born approximation using plane waves, Byron and Joachain as well as Le Sech and correlated BBK-type wave functions
respectively for incident and scattered, bound and ejected electrons. The angular distribution of FDCS of our calculation
is presented in various modes of coplanar geometry and comparison is made with the available experimental data. We observe
that the present calculation is able to reproduce the trend of the experimental data. However, it differs in magnitude from
the experiment. The present theory does not predict four-peak structure insummed mutual angle mode for lower excess ejected electron energies. We also discuss the importance of momentum transfer, post-collision interaction
(PCI) and ion participation in the (e,3e) process in constant θ12 mode 相似文献
3.
Cestmir Burdik Sergey Krivonos Andrey Shcherbakov 《Czechoslovak Journal of Physics》2005,55(11):1357-1364
We show that it is possible to construct a supersymmetric mechanics with four supercharges possessing not conformally flat
target space. A general idea of constructing such models is presented. A particular case with Eguchi-Hanson target space is
investigated in detail: we present the standard and quotient approaches to get the Eguchi-Hanson model, demonstrate their
equivalence, give a full set of nonlinear constraints, study their properties and give an explicit expression for the target
space metric.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
4.
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
5.
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
6.
Decay properties of <Emphasis Type="Italic">N</Emphasis>∼<Emphasis Type="Italic">Z</Emphasis> nuclei
E. Roeckl 《Physics of Atomic Nuclei》2002,65(4):689-696
By using heavy-ion induced fusion-evaporation reactions at the on-line mass separator of GSI, the decay properties of neutron-deficient isotopes between 56Ni and 100Sn were investigated. The experimental results will be presented and discussed in comparison with model predictions. 相似文献
7.
Through phase transformation kinetic analysis and experimental observation, the δ/γ transformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated. According to JMA solid-state transformation kinetic theory, the Time-Temperature-Transformation (TTT) curves of the δ/γ transformation in peritectic Fe-Ni alloy were calculated. On this basis, the physical correlation between the δ/γ transformation and the initial undercooling of melt (△T) was elucidated. The results indicate that the change of △T can alter not only the overall δ/γ transformation pathways but also the transformation fraction with respect to each transformation mechanism. 相似文献
8.
Though the predictions of the standard model (SM) are in excellent agreement with experiments, there are still several theoretical
problems associated with the Higgs sector of the SM, where it is widely believed that some new physics will take over at the
TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we have investigated
the effects of the LH model on γγ → γγ scattering [1].
相似文献
9.
Ctirad Klimčík 《International Journal of Theoretical Physics》2007,46(10):2443-2463
We show that D-branes in the Euclidean AdS
3 can be naturally associated to the maximally isotropic subgroups of the Lu–Weinstein double of SU(2). This picture makes very transparent the residual loop group symmetry of the D-brane configurations and gives also immediately the D-branes shapes and the σ-model boundary conditions in the de Sitter T-dual of the SL(2,C)/SU(2) WZW model. 相似文献
10.
11.
C. Albertus J. M. Flynn E. Hernández J. Nieves J. M. Verde-Velasco 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):725-727
The semileptonic decay B→π is studied starting from a simple quark model that takes into into account the effect of the B*-resonance. A novel, multiply subtracted, Omnès dispersion relation has been implemented to extend the predictions of the
quark model to all q2 values accessible in the physical decay. By comparison to the experimental data, we extract | V
ub| = (3.4±0.2(exp.)±0.7(theory))0-3. As a further test of the model, we have also studied D→π and D→K decays for which we get good agreement with experiment. 相似文献
12.
13.
E. P. Shabalin 《Physics of Atomic Nuclei》2008,71(6):1036-1039
Contrary to widespread opinion that the final-state interaction (FSI) enlarges the amplitude 〈2π; I = 0|K
0〉, we argue that FSI is not able to increase the absolute value of this amplitude.
The text was submitted by the author in English. 相似文献
14.
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
15.
Some of the basic problems in neutrino physics, such as new energy scales, the enormous gap between the neutrino masses and
the lightest charged fermion mass, and the possible existence of sterile neutrinos in the eV mass range are studied in the
local gauge group SU
L
(4)×U(1) for electroweak unification, which does not contain fermions with exotic electric charges. It is shown that the neutrino
mass spectrum can be decoupled from that of the other fermions. The further normal seesaw mechanism for neutrinos, with right-handed
neutrino Majorana masses of order M≫M
weak as well a new eV-scale can be accommodated. The eV-scale seesaw may manifest itself in experiments like the Liquid Scintillation
Neutrino Detector (LSND) and MiniBooNE (MB) experimental results and future neutrino experiments. 相似文献
16.
H.-Y. Cheng 《The European Physical Journal C - Particles and Fields》2003,26(4):551-565
Based on SU(3) flavor symmetry, many of the quark-graph amplitudes in two-body non-leptonic decays of charmed mesons can
be extracted from experiment, which enable us to see the relevance and importance of weak annihilation topologies and to determine
the complex parameters a1 and a2 to test the factorization approach. It is found that a
2
/a
1
in and can be different by a factor of 2, indicating that non-factorizable corrections to the latter are far more important than
the former. The relative phase between a1 and a2 is about 150°. Weak annihilation topologies induced by nearby resonances via final-state rescattering can be described in
a model-independent manner. Although the W-exchange contribution in decays is dominated by resonant final-state interactions (FSIs), its amplitude in VP decays (V: vector meson, P: pseudoscalar meson) receives little contributions from FSIs in the quark-antiquark resonance formation. As a consequence,
the sign flip of the W-exchange amplitude in and decays, which is needed to explain the relatively real decay amplitudes of , remains unexplained. SU(3) symmetry is badly broken in some Cabibbo-suppressed modes and this can be accounted for by the
accumulation of some modest SU(3) violation in individual quark-graph amplitudes.
Received: 19 July 2002 / Published online: 20 November 2002 相似文献
17.
18.
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
19.
20.
The properties of polycrystalline CdTe with a grain size of 5–30 μm have been investigated using the microphotoluminescence
methods of spectral analysis and topography. This material has been prepared by direct synthesis in a vapor flow of components
at a low temperature. The dominance of the Y and Z bands in the spectra reflects a nonequilibrium character of the crystallization processes. The superlinear dependences of
the luminescence intensity on the level of the band-to-band excitation indicate the exciton nature of the corresponding transitions.
The activation energies for temperature quenching of luminescence in the temperature range T = 100–150 K are found to be 120 meV for the Y luminescence and 180 meV for the Z luminescence, which correspond to the dissociation of excitons bound to defects with the transition of charge carriers to
the conduction and valence bands. The monochromatic topography data indicate that Y and Z defects have different material bases. 相似文献