共查询到20条相似文献,搜索用时 31 毫秒
1.
J. L. Goity 《Physics of Atomic Nuclei》2005,68(4):624-633
The 1/N c -power countings for baryon decays and configuration mixings are determined by means of a nonrelativistic quark picture. Such countings are expected to be robust under changes in the quark masses and, therefore, valid as these become light. It is shown that excited baryons have natural widths of \(\mathcal{O}(N_c^0 )\). These dominant widths are due to the decays that proceed directly to the ground-state baryons, with cascade decays being suppressed to \(\mathcal{O}(1/N_c )\). Configuration mixings, defined as mixings between states belonging to different O(3) × SU(2N f ) multiplets, are shown to be subleading in an expansion in \(1/\sqrt {N_c }\) when they involve the ground-state baryons, while the mixings between excited states can be \(\mathcal{O}(N_c^0 )\). 相似文献
2.
V. V. Pokropivny L. I. Ovsyannikova S. V. Kovrigin 《Physics of the Solid State》2007,49(12):2335-2341
A general approach is formulated to the design of crystal-forming fullerene-like clusters X n Y n from which zeolite-like covalent crystals based on IV-IV, III-V, and II-VI binary semiconductor compounds with diamond-like sp 3 bonds can be constructed and synthesized by means of copolymerization through faces. A number of the smallest sized crystal-forming boron nitride clusters are constructed, such as the B12N12, B16N16, B18N18, B24N24, B36N36, and B 60N60 fulborenes. The optimized configurations, electronic structures, charge transfers, band gaps, total energies, cohesive energies, and electron density maps of the clusters are calculated using the spin-restricted Hartree-Fock method in the 6–31G basis set. Comparative calculations of the B60N60 fulborene with the use of the density functional theory method have demonstrated that the spin-restricted Hartree-Fock method in the 6–31G basis set is optimum from the standpoint of the accuracy and efficiency. 相似文献
3.
During the last decade, as the experimental and computing means and techniques have rapidly evolved, the experimental investigation of the f7/2-shell nuclei has gained renewed interest. TheN = Z nuclei studied with the GASP array range from 44Ti to 52Fe. The results extended the knowledge of their structure up to high spins and excitation energies, above band terminations, where the competition with the charged-particles emission was initially thought to obscure the possibility of gamma-ray spectroscopy investigation. The paper highlights some of the most outstanding properties of these nuclei such as the nuclear rotation and backbending effects, band termination states, yrast traps, non-natural parity bands, competition between T = 0 and T = 1 pn pairing modes.Received: 30 October 2002, Published online: 16 March 2004PACS:
21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Cs Shell model - 23.20.Lv
transitions and level energies - 27.40. + z
C.A. Ur: On leave from NIPNE Bucharest, Romania 相似文献
4.
The hierarchical structure of fermion masses of the Standard Model is explained in split fermion models by localizing the
fermions at different points in an extra dimension. We consider split fermion models with two bulk scalars compactified on an orbifold. In the static case we find analytical expression for the localizer. We also address the issue of stability of the localizer.
We also find exact solutions for the fermion zero modes. We explore the parameter space of the model. We find ample opportunity
for construction of phenomenologically viable theories exist. 相似文献
5.
J. Gasser B. Kubis N. Paver M. Verbeni 《The European Physical Journal C - Particles and Fields》2005,40(2):205-227
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for
decays. Special emphasis is given to the stability of the inner bremsstrahlung-dominated relative branching ratio versus the K
e3 form factors, and on the separation of the structure-dependent amplitude in differential distributions over the phase space. For the structure-dependent terms, an assessment of the order p
6 corrections is given, in particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.Received: 9 December 2004, Published online: 21 February 2005PACS:
13.20.Eb, 11.30.Rd, 12.39.Fe 相似文献
6.
M. A. Braun 《The European Physical Journal C - Particles and Fields》2009,63(2):287-296
The lowest order pomeron loop is calculated for the leading conformal weight with full dependence of the triple-pomeron vertex
on intermediate conformal weights. The loop is found to be convergent. Its contribution to the pomeron Green function begins
to dominate already at rapidities 10–15. The pomeron pole renormalization is found to be quite small due to a rapid fall of
the triple-pomeron vertex with rising conformal weights. 相似文献
7.
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9.
J. P. Guedes S. Azevedo M. Machado 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):127-135
We have studied, through ab initio calculations, the stability of 60° and 120° boron nitride nanocones containing mono and
multiple boron, nitrogen, and
carbon vacancies. The stability of the vacancies as well as the structures reconstruction mechanism have been investigated.
Our results indicate that the
stability of the cones presenting such vacancies strongly depends on growth conditions. We have also found that multiple vacancies
display formation energies that
are comparable, and in some cases, even lower to the ones presented by monovacancies. Therefore, our results allow us to conclude
that the formation energy does not
depend on the vacancy size. Finally, for 120° cones, we can verify that the stability of the boron and nitrogen vacancies
depends on the position where the atom has
been removed. 相似文献
10.
V. Cirigliano H. Neufeld H. Pichl 《The European Physical Journal C - Particles and Fields》2004,35(1):53-65
We present a detailed numerical study of the Ke3 decays to
in chiral perturbation theory with virtual photons and leptons. We describe the extraction of the CKM matrix element |Vus| from the experimental Ke3 decay parameters. We propose a consistency check of the K + e3 and K0e3 data that is largely insensitive to the dominating theoretical uncertainties, in particular the contributions of
. Our analysis is highly relevant in view of the recent high statistics measurement of the K + e3 branching ratio by E865 at Brookhaven which does not indicate any significant deviation from CKM unitarity but rather a discrepancy with the present K0e3 data.Received: 22 January 2004, Published online: 30 April 2004Work supported in part by IHP-RTN, Contract No. HPRN-CT2002-00311 (EURIDICE) and by Acciones Integradas, Project No. 19/2003 (Austria), HU2002-0044 (MCYT, Spain) 相似文献
11.
E. R. Podolyak 《Journal of Experimental and Theoretical Physics》2011,113(6):1035-1039
The emergence of surface superconductivity in a type I superconductor is considered taking into account the surface free energy
of the superconducting phase. It is shown that the disregard of the surface energy leads to a substantial error in determining
the Ginzburg-Landau parameter from the measurements of the H
c3 field. 相似文献
12.
Ginzburg-Landau (GL) theory is used to study surface superconductivity for UPt3 for various order parameter symmetries (OPS), andH c3 is found for all principal directions of the surface normal\(\hat n\) and the field [1]. Assuming specular reflection, and allowing for reorientation of the antiferromagnetic symmetry breaking field in the models withE 1g ,E 2g ,E 1u , orE 2u symmetry, the experiments of Keller et al. [2] with\(\hat n = \hat a\) can be qualitatively explained for all OPS except possiblyA 1u ⊕B 1u . The implied GL parameters then predict qualitatively different and OPS dependent behavior for\(\hat n = \hat a^* \) and\(\hat n = \hat c\). Study ofH c3 for these surfaces would give strong clues about the OPS of UPt3. 相似文献
13.
14.
Reactions of (N-isocyanimino)triphenylphosphorane with N,N-dicyclohexylcarbodiimide in the presence of aromatic (or heteroaromatic) carboxylic acids proceed smoothly at room temperature and in neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions, and no side reactions were observed. 相似文献
15.
P. V. Zakharov M. D. Starostenkov S. V. Dmitriev 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(11):1322-1326
The conditions for the existence of discrete breathers (DBs) in biatomic crystals of AB and A 3 B composition are established, and their properties are studied by means of molecular mechanics using the examples of CuAu and Pt3Al, respectively. The phonon spectra of the crystals are analyzed, and a gap in the phonon spectrum of CuAu is obtained via considerable homogeneous elastic strain. There is a gap in the phonon spectrum of the Pt3Al crystal at zero strain, due to the considerable difference between the atomic weights of its components. The frequencies at which discrete breathers can exist in the considered crystals are determined. The energy localized on different types of DBs is estimated. The propagation of a current pulse through Pt3Al resulting in the excitation of DBs with mild nonlinearity is simulated. 相似文献
16.
The spatial string tension across a crossover from the low-temperature phase to the high-temperature phase is computed in
QCD with two flavors of nonperturbatively improved Wilson fermions at small lattice spacing a ∼ 0.12 fm. We find that in the low-temperature phase spatial string tension agrees well with zero-temperature string tension.
Furthermore, it does not show increasing for temperatures up to T = 1.36T
pc, the highest temperature considered. Our results agree with some theoretical predictions.
The text was submitted by the authors in English. 相似文献
17.
O. P. Yushchenko V. F. Kurshetsov A. P. Filin S. A. Akimenko A. V. Artamonov A. M. Blik V. V. Brekhovskikh V. S. Burtovoy S. V. Donskov A. V. Inyakin A. M. Gorin G. V. Khaustov S. A. Kholodenko V. N. Kolosov A. S. Konstantinov V. M. Leontiev V. A. Lishin M. V. Medynsky Yu. V. Mikhailov V. F. Obraztsov V. A. Polyakov A. V. Popov V. I. Romanovsky V. I. Rykalin A. S. Sadovsky V. D. Samoilenko V. K. Semenov O. V. Stenyakin O. G. Tchikilev V. A. Uvarov V. A. Duk S. N. Filippov E. N. Guschin Yu. G. Kudenko A. A. Khudyakov V. I. Kravtsov A. Yu. Polyarush V. N. Bychkov G. D. Kekelidze V. M. Lysan B. Zh. Zalikhanov 《JETP Letters》2018,107(3):139-142
Recent results from OKA setup concerning form factor studies in Ke3 decay are presented. About 5.25 M events obtained for decays of 17.7 GeV/cK+ are selected for the analysis. The linear and quadratic slopes for the decay form factor f+(t) are measured: λ'+ = 2.95 ± 0.022 ± 0.018 × 10 -2 for the linear slope fit and λ+ = 2.611 ± 0.035 ± 0.028 × 10 -2, λ"+ = 1.91 ± 0.19 ± 0.14 × 10 -3 for the quadratic one. The scalar and tensor contributions are compatible with zero. Several alternative parametrizations are tried: the Pole fit parameter is found to be M V = 891 ± 3 MeV; the parameter of the dispersive parametrization is measured to be Λ+ = 2.458 ± 0.018 × 10-2. 相似文献
18.
Necessary and sufficient conditions to the existence of a hermitian connection with totally skew-symmetric torsion and holonomy contained in SU(3) are given. A formula for the Riemannian scalar curvature is obtained. Non-compact solution to the supergravity-type I equations of motion with non-zero flux and non-constant dilaton is found in dimension 6. Non-conformally flat non-compact solutions to the supergravity-type I equations of motion with non-zero flux and non-constant dilaton are found in dimensions 7 and 8. A Riemannian metric with holonomy contained in G2 arises from our considerations and Hitchin’s flow equations, which seems to be new. Compact examples of SU(3),G2 and Spin(7) instanton satisfying the anomaly cancellation conditions are presented. 相似文献
19.
F. Finkel D. Gómez-Ullate A. González-López M.A. Rodríguez R. Zhdanov 《Communications in Mathematical Physics》2003,233(2):191-209
The B
N
hyperbolic Sutherland spin model is expressed in terms of a suitable set of commuting Dunkl operators. This fact is exploited
to derive a complete family of commuting integrals of motion of the model, thus establishing its integrability. The Dunkl
operators are shown to possess a common flag of invariant finite-dimensional linear spaces of smooth scalar functions. This
implies that the Hamiltonian of the model preserves a corresponding flag of smooth spin functions. The discrete spectrum of
the restriction of the Hamiltonian to this spin flag is explicitly computed by triangularization. The integrability of the
hyperbolic Sutherland spin chain of B
N
type associated with the dynamical model is proved using Polychronakos's ``freezing trick'.
Received: 14 February 2002 / Accepted: 19 June 2002 Published online: 10 December 2002
RID="*"
ID="*" Corresponding author. E-mail: artemio@fis.ucm.es
RID="**"
ID="**" On leave of absence from Institute of Mathematics, 3 Tereschenkivska St., 01601 Kyiv-4 Ukraine
Communicated by L. Takhtajan 相似文献
20.
We discuss the quantum state structure using the standard model for three colored quarks in the fundamental representations of SU(3)c making up the singlet ground state of the hadrons. This allows us to calculate a finite von Neumann entropy from the quantum reduced density matrix, which we explicitly evaluate for the quarks in a model for the meson and baryon states.Received: 9 December 2003, Revised: 23 January 2004, Published online: 8 April 2004D.E. Miller: om0@psu.eduPermanent address: Department of Physics, Pennsylvania State University, Hazleton Campus, Hazleton, Pennsylvania, 18201 USA 相似文献