Quantum trajectories of photoluminescence of <Emphasis Type="Italic">F</Emphasis> <Subscript>2</Subscript> centers in a LiF crystal

Single F₂ color centers in a LiF crystal are studied by means of fluorescence microscopy with analysis and statistical processing of the time trajectories of fluorescence intensity. It is shown that a color center subjected to photoirradiation can enter a triplet state with a subsequent transition to a mobile state in which the center is reoriented.     

Quantum trajectories of the photoluminescence of <Emphasis Type="Italic">F</Emphasis> <Subscript>2</Subscript> centers in a LiF crystal

The rate of intercombination transitions for single F₂ color centers in a LiF crystal is estimated, in order of magnitude, as Γ_TS ～ 10⁴ transitions/s using the results from the computer modeling of quantum trajectories of photoluminescence intensity of these centers. The lifetime of an F₂ center in the first triplet state is found to be equal to 6.9 ± 0.7 s.     

Fermion Localization on the <Emphasis Type="Italic">orbifold</Emphasis><Emphasis Type="Italic">S</Emphasis><Subscript>1</Subscript>/<Emphasis Type="Italic">Z</Emphasis><Subscript>2</Subscript>

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.     

Discrete breathers in biatomic crystals of <Emphasis Type="Italic">AB</Emphasis> and <Emphasis Type="Italic">A</Emphasis><Subscript>3</Subscript><Emphasis Type="Italic">B</Emphasis> composition

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.     

A Geometric Construction of the Exceptional Lie Algebras <Emphasis Type="Italic">F</Emphasis><Subscript>4</Subscript> and <Emphasis Type="Italic">E</Emphasis><Subscript>8</Subscript>

We present a geometric construction of the exceptional Lie algebras F ₄ and E ₈ starting from the round spheres S ⁸ and S ¹⁵, respectively, inspired by the construction of the Killing superalgebra of a supersymmetric supergravity background.     

On the 2<Emphasis Type="Italic">s</Emphasis>-like relaxed excited state of the <Emphasis Type="Italic">F</Emphasis> center in alkali halide crystals

The energy and spectroscopic characteristics of the first excited 2s-like electron state of the F center are presented according to the calculations performed in the framework of the variational model proposed by Gourary and Adrian. The relaxation of the crystal lattice in the vicinity of the excited F center is described. The problem of the spatial propagation of the F center is discussed. The results obtained for the 2p and 2s states of the F center are compared with each other and with the relevant experimental data.     

Accelerating universe from <Emphasis Type="Italic">F</Emphasis>(<Emphasis Type="Italic">T</Emphasis>) gravity

It is shown that the acceleration of the universe can be understood by considering a F(T) gravity models. For these F(T) gravity models, a variant of the accelerating cosmology reconstruction program is developed. Some explicit examples of F(T) are reconstructed from the background FRW expansion history.     

Analysis of the logarithmic slope of <Emphasis Type="Italic">F</Emphasis><Subscript>2</Subscript> from the Regge gluon density behavior at small <Emphasis Type="Italic">x</Emphasis>

We study the accuracy of the Regge behavior of the gluon distribution function for an approximate relation that is frequently used to extract the logarithmic slopes of the structure function from the gluon distribution at small x. We show that the Regge behavior analysis results are comparable with HERA data and are also better than other methods that expand the gluon density at distinct points of expansion. We also show that for Q ² = 22.4 GeV², the x dependence of the data is well described by gluon shadowing corrections to the GLR-MQ equation. The resulting analytic expression allows us to predict the logarithmic derivative ∂F ₂(x, Q ²)/∂lnQ ² and to compare the results with the H1 data and a QCD analysis fit with the MRST parameterization input.     

Interacting Dark Energy in the Dark <Emphasis Type="Italic">S</Emphasis><Emphasis Type="Italic">U</Emphasis>(2)<Subscript><Emphasis Type="Italic">R</Emphasis></Subscript> Model

We explore the cosmological implications of the interactions among the dark particles in the dark SU(2) _R model. It turns out that the relevant interaction is between dark energy and dark matter, through a decay process. With respect to the standard ΛCDM model, it changes only the background equations. We note that the observational aspects of the model are dominated by degeneracies between the parameters that describe the process. Thus, only the usual Λ CDM parameters such as the Hubble expansion rate and the dark energy density parameter (interpreted as the combination of the densities of the dark energy doublet) could be constrained by observations at this moment.     

The Dirac Operator on <Emphasis Type="Italic">SU</Emphasis><Subscript><Emphasis Type="Italic">q</Emphasis></Subscript>(2)

We construct a 3⁺-summable spectral triple over the quantum group SU_q(2) which is equivariant with respect to a left and a right action of The geometry is isospectral to the classical case since the spectrum of the operator D is the same as that of the usual Dirac operator on the 3-dimensional round sphere. The presence of an equivariant real structure J demands a modification in the axiomatic framework of spectral geometry, whereby the commutant and first-order properties need be satisfied only modulo infinitesimals of arbitrary high order.Partially supported by Polish State Committee for Scientific Research (KBN) under grant 2 P03B 022 25.Regular Associate of the Abdus Salam ICTP, Trieste.     

Spectral Action on <Emphasis Type="Italic">SU</Emphasis><Subscript><Emphasis Type="Italic">q</Emphasis></Subscript>(2)

The spectral action on the equivariant real spectral triple over is computed explicitly. Properties of the differential calculus arising from the Dirac operator are studied and the results are compared to the commutative case of the sphere . UMR 6207, – Unité Mixte de Recherche du CNRS et des Universités Aix-Marseille I, Aix-Marseille II et de l’Université du Sud Toulon-Var, Laboratoire affilié à la FRUMAM – FR 2291. Partially supported by Polish Government grants 189/6.PRUE/2007/7; 115/E-343/SPB/6.PR UE/DIE and N 201 1770 33.     

The <Emphasis Type="Italic">q</Emphasis>-boson-fermion realizations of the quantum superalgebra <Emphasis Type="Italic">U</Emphasis><Subscript><Emphasis Type="Italic">q</Emphasis></Subscript>(<Emphasis Type="Italic">osp</Emphasis>(1/2))

We show that our construction of realizations for algebras and quantum algebras can be generalized to quantum superalgebras too. We studyan example of quantum superalgebra U _q (osp(1/2)) and give the boson-fermion realization with respect to one pair of q-boson operators and one pair of fermions.     

Longitudinal structure function <Emphasis Type="Italic">F</Emphasis><Subscript>L</Subscript>: Perturbative QCD and <Emphasis Type="Italic">k</Emphasis><Subscript>T</Subscript>-factorization versus experimental data at fixed <Emphasis Type="Italic">W</Emphasis>

We use the results for the structure function F_L for a gluon target with a nonzero transverse momentum squared at the order α_s, obtained in our previous paper, for comparison with recent H1 experimental data for F_L at fixed W values and with collinear GRV predictions in the leading-order and next-to-leading-order approximations.     

Summary on high <Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> probes

Results on high-p _T probes shown at the Hard Probes 2008 Conference are summarized, with an appreciation of the improvements in precision of the measurements and experimental techniques since the beginning of RHIC operation. Particular attention is given to the latest measurements of the nuclear modification factor of identified particles, photon-hadron correlation measurements, and full jet reconstruction.     

The <Emphasis Type="Italic">N</Emphasis> = <Emphasis Type="Italic">Z</Emphasis><Emphasis Type="Italic">f</Emphasis><Subscript>7/2</Subscript>-shell nuclei: Experimental highlights

During the last decade, as the experimental and computing means and techniques have rapidly evolved, the experimental investigation of the f_7/2-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     

<Emphasis Type="Italic">SU</Emphasis>(3)-Instantons and <Emphasis Type="Italic">G</Emphasis><Subscript>2</Subscript>,<Emphasis Type="Italic">Spin</Emphasis>(7)-Heterotic String Solitons

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.     

Radiative <Emphasis Type="Italic">K</Emphasis><Subscript><Emphasis Type="Italic">e</Emphasis>3</Subscript> decays revisited

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     

Polynomial Realization of <Emphasis Type="Italic">s</Emphasis>l<Subscript><Emphasis Type="Italic">q</Emphasis></Subscript>(2) and Fusion Rules at Exceptional Values of <Emphasis Type="Italic">q</Emphasis>

Representations of the sℓ_q(2) algebra are constructed in the space of polynomials of real (complex) variable for q^N=1. The spin addition rule based on eigenvalues of Casimir operator is illustrated on few simplest cases and conjecture for general case is formulated.