SU(2)L×SU(2)R×U(1) gauge model

We determine here the most general electroweak interaction based on the groupSU(2)_L×SU(2)_R×U(1). When we rotate theZ ₁,Z ₂ basis to theZ,D basis such that the total interaction ofZ with the right-handed current is zero, we obtain an interaction that is free of triangle anomalies. This condition enables us to know the angle through whichZ ₁,Z ₂ basis is to be rotated. We show that the triangle anomaly free interaction obtained by others is contained here as a special case. We also determine the triangle anomaly free weak interaction whenever the neutral (Z,D) bosons are mass eigenstates and show that it reduces to the neutral sector of the standard model whenever g _R ² goes to infinity. The charged sector is also developed here. The most general elements of the masssquared matrix of theZ,D bosons are evaluated. The masses of the left- and right-handed charged bosons are also determined.     

A wire trap for neutral atoms

We present new ways of trapping a neutral atom with static electric and magnetic fields. We discuss the interaction of a neutral atom with the magnetic field of a current carrying wire and the electric field of a charged wire. Atoms can be trapped by the 1/r magnetic field of a current-carrying wire in a two-dimensional trap. The atoms move in Kepler-like orbits around the wire and angular momentum prevents them from being absorbed at the wire. Trapping was demonstrated in an experiment by guiding atoms along a 1 m long current-carrying wire. Stable traps using the interaction of a polarizable atom with the electric field of a charged wire alone are not possible because of the 1/r ² form of the interaction potential. Nevertheless, we show that one can build a microscopic trap with a combination of a magnetic field generated by a current in a straight wire and the static electric field generated by a concentric charged ring which provides the longitudinal confinement. In all of these traps, the neutral atoms are trapped in a region of maximal field, in theirhigh-field seeking state.Dedicated to H. Walther on the occasion of his 60th birthday     

Interacting entropy-corrected holographic dark energy with apparent horizon as an infrared cutoff

In this work we consider the entropy-corrected version of interacting holographic dark energy (HDE), in the non-flat universe enclosed by apparent horizon. Two corrections of entropy so-called logarithmic ‘LEC’ and power-law ‘PLEC’ in HDE model with apparent horizon as an IR-cutoff are studied. The ratio of dark matter to dark energy densities u, equation of state parameter w _D and deceleration parameter q are obtained. We show that the cosmic coincidence problem is solved for interacting models. By studying the effect of interaction in EoS parameter of both models, we see that the phantom divide may be crossed and also understand that the interacting models can drive an acceleration expansion at the present and future, while in non-interacting case, this expansion can happen only at the early time. The graphs of deceleration parameter for interacting models, show that the present acceleration expansion is preceded by a sufficiently long period deceleration at past. Moreover, the thermodynamical interpretation of interaction between LECHDE and dark matter is described. We obtain a relation between the interaction term of dark components and thermal fluctuation in a non-flat universe, bounded by the apparent horizon. In limiting case, for ordinary HDE, the relation of interaction term versus thermal fluctuation is also calculated.     

Stronger neutrino interactions at extremely high energies and the muon anomalous magnetic moment

A specific model of parity-conserving lepton substructure is considered. We show that a positive-definite contribution to the muon at the possible level of about can be related to a significant increase in the interaction cross section for cosmic-ray neutrinos with energies above about eV. The additional cross section at eV is calculated to be cm, which is about 100 times the standard weak-interaction cross section. The model involves an extremely massive, neutral lepton, with GeV fixed by the new contribution to . Received: 28 May 2001 / Revised version: 13 November 2001 / Published online: 11 January 2002     

Elusive <Emphasis Type="Italic">s-f</Emphasis> intrasite interactions and double exchange in solids: Ferromagnetic versus nonmagnetic ground state

From the theory of many-electron states in atoms, we know that there exists a strong Coulomb repulsion, which results in the electronic term structure of atoms and is responsible for Hund’s rules. By expanding the Coulomb on-site repulsion into a multipolar series, we derive this interaction and show that it is also present in solids as a correlation effect, which means that the interaction requires a multideterminant version of the Hartree-Fock method. Of particular interest is the case where this interaction couples states of localized (f) and delocalized (s) electrons. We show that the interaction is bilinear in the creation/annihilation operators for localized electrons and bilinear in the operators for conduction electrons. To study the coupling, we consider a simple model in the framework of an effective limited configuration interaction method with one localized f-electron and one itinerant s-electron per crystal site. The on-site multipole interaction between the f- and s-electrons is explicitly taken into account. It is shown that depending on the low-lying excitation spectrum imposed by the crystal electric field, the model can lead not only to ferromagnetism but also to a nonmagnetic state. The model is relevant for solids with localized and itinerant electron states.     

Effect of channelben protein interaction on translocation of a protein-like chain through a finite channel

We study the translocation of a protein-like chain through a finite cylindrical channel using the pruned-enriched Rosenbluth method (PERM) and the modified orientation-dependent monomer-monomer interaction (ODI) model. Attractive channels (ε_cp=-2.0, -1.0, -0.5), repulsive channels (ε_cp=0.5, 1.0, 2.0), and a neutral channel (ε_cp =0) are discussed. The results of the chain dimension and the energy show that Z₀=1.0 is an important case to distinguish the types of the channels. For the strong attractive channel, more contacts form during the process of translocation. It is also found that an external force is needed to drive the chain outside of the channel with the strong attraction. While for the neutral, the repulsive, and the weak attractive channels, the translocation is spontaneous.     

The Pauli Principle and the Restricted Primitive Model

The restricted primitive model is an electrically neutral, classical model consisting of hard spheres charged either +q or –q. We show that, by appropriately selecting the diameter of the hard spheres, the pressure when q=0 can be made equal to that for a fluid of Maxwell–Boltzmann point ions and an ideal Fermi gas of electrons. We compare the series expansion of these classical and quantum systems and find that, except for intermediate de Broglie density and moderate to strong electrical interaction strength, the restricted primitive model gives a reasonable representation of the pressure of the corresponding quantum system. Much of the current interest, however, has been focused on the above, excepted region.     

Four-quark final state in W-pair production: Case of signal and background

We discuss theoretical predictions for -pair production and decay at LEP2 and higher energies in a form suitable for comparison with raw data. We present a practical framework for calculating uncertainties of predictions given by the KORALW and grc4f Monte Carlo programs. As an example we use observables in the decay channel: the total four-quark (four-jet) cross section and two-quark/jet invariant-mass distribution and cross section, in the case when the other two may escape detection. Effects of QED bremsstrahlung, effective couplings, running and widths, Coulomb interaction and the complete tree level set of diagrams are discussed. We also revisit the question of technical precision of the new version 1.21 of the KORALW Monte Carlo code as well as of version 1.2(26) of the grc4f one. Finally we find predictions of the two programs to have an overall physical uncertainty of 2%. As a side result we show, on the example of an invariant mass distribution, the strong interplay of spin correlations and detector cut-offs in the case of four-fermion final states. Received: 18 March 1997 / Revised version: 4 July 1997     

Voltage-controlled optics of a quantum dot

We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with approximately 2 mueV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a mueV energy scale.     

Holonomic quantum computation based on the scalar Aharonov–Bohm effect for neutral particles and linear topological defects

We discuss holonomic quantum computation based on the scalar Aharonov–Bohm effect for a neutral particle. We show that the interaction between the magnetic dipole moment and external fields yields a non-abelian quantum phase allowing us to make any arbitrary rotation on a one-qubit. Moreover, we show that the interaction between the magnetic dipole moment and a magnetic field in the presence of a topological defect yields an analogue effect of the scalar Aharonov–Bohm effect for a neutral particle, and a new way of building one-qubit quantum gates.     

A simple construction of ellipticR-matrices

We show that Belavin's solutions of the quantum Yang-Baxter equation can be obtained by restricting an infiniteR-matrix to suitable finite-dimensional subspaces. This infiniteR-matrix is a modified version of the Shibukawa-UenoR-matrix acting on functions of two variables.     

Bremsstrahlung by neutral atomic nitrogen

We show that the strong absorption resonances in bremsstrahlung by electrons in the field of neutral nitrogen atoms predicted in an earlier paper⁽¹⁾ are removed by the inclusion of configuration interaction in continuum wave functions.     

Analysis of the neutral-current interaction in the inclusive neutrino reactions

We attempt a general phenomenological analysis of the neutral weak current in the inclusive neutrino reactions using the parton model as a tool. From the recently reported data on these processes we determine the strengthH of the neutral-current interaction as well as the amount of theVA interference. We find (H/G)²=0·54±0·06 whereG is the Fermi coupling constant and theVA interference contribution turns out to be 33±23%. We also discuss the comparison of the data with various models for the neutral hadronic current. An erratum to this article is available at .     

Light-induced effect on the density distribution in a sample of cold trapped atoms

As it is known [1] an intense laser field can induce atom-atom interaction according to a dipole-dipole R ^–3 law. Such an interaction depends on the angle between light polarization and interatomic vector-position R. This angular dependence may produce an anisotropy in the spatial density distribution of the confined sample of cold atoms. We develop the main relations and apply them to the case of an atomic cloud of cold trapped neutral atoms with the density higher than or of the order of ^–3, where is the wavelength of light. The results presented here show the effect of such an interaction in a density regime of high experimental interest.     

Extracting Information About Few-Body Breakup Thresholds from High-Energy Collisions

We show that the analysis of high-energy collisions provides an alternative, and sometimes advantageous, method of gathering information on a breakup system at threshold. We demonstrate the applicability of this approach by extracting the s-wave scattering length a₀ for the collision of electrons by neutral atoms in metastable states from measurements of photo- and collisional detachment of electrons from negative ions and electron capture to continuum states of neutral projectiles in atomic ionization collisions. Finally, we discuss how to generalize these ideas to gather information about an N-body threshold behavior.Fax: +54 2944 445299, Phone: +54 2944 445234     

Signature of the ηNN configurations in coherent πphotoproduction on the deuteron

The photoproduction of a neutral pion on the deuteron is considered in the energy region around the η threshold, where a bump-like structure was observed at very backward pion angles. Different dynamical aspects which may be responsible for this phenomenon are analysed within a theoretical frame which includes intermediate ηNN configurations. The results show, in particular, that a three-body treatment of the ηNN interaction is of special importance.     

Infinite slabs and other weird plane symmetric space–times with constant positive density

We present the exact solution of Einstein’s equation corresponding to a static and plane symmetric distribution of matter with constant positive density located below z = 0. This solution depends essentially on two constants: the density ρ and a parameter κ. We show that these space–times finish down below at an inner singularity at finite depth. We show that for κ ≥ 0.3513 . . . the dominant energy condition is satisfied all over the space–time. We match this solution to the vacuum one and compute the external gravitational field in terms of slab’s parameters. Depending on the value of κ, these slabs can be attractive, repulsive or neutral. In the first case, the space–time also finishes up above at an empty repelling singular boundary. In the other cases, they turn out to be semi-infinite and asymptotically flat when z → ∞. We also find solutions consisting of joining an attractive slab and a repulsive one, and two neutral ones. We also discuss how to assemble a “gravitational capacitor” by inserting a slice of vacuum between two such slabs.     

Rare decay B\rightarrow X_sl^+l^- in a CP spontaneously broken two-Higgs doublet model

The Higgs boson mass spectrum and couplings of the neutral Higgs bosons to the fermions are worked out in a CP spontaneously broken two-Higgs doublet model in the large case. The differential branching ratio, forward-backward asymmetry, CP asymmetry and lepton polarization for are computed. It is shown that the effects of neutral Higgs bosons are quite significant when is large. Especially, the CP violating normal polarization can be as large as several percents. Received: 15 October 2001 / Revised version: 5 March 2002 / Published online: 26 July 2002     

2nd Class Currents in Neutrino Reactions

The influence of 2nd class currents in neutrino reactions is investigated. We show that WEINBERG'S unified model of electromagnetic and weak interactions implies both neutral and 2nd class currents. Possible experimental effects due to 2nd class neutral weak currents are discussed. Further, we investigate implications of 2nd class charged currents for hadronic neutral weak currents. It is shown that if 2nd class charged currents exist, the isospin I = 1 axial-vector neutral current must be a “new” current, or it must contain a “new” I = 1 part. 2nd class charged currents are excluded if the I = 1 axial-vector neutral current is “old”, i.e., if it is proportional to the third component of the charged current. Then also the proportionality constant is real. CP invariance is assumed throughout the discussion.     

Implications of the precision data for very light Higgs Boson scenarios in 2HDM(II)

We present an up-to-date analysis of the constraints the precision data impose on the (CP-conserving) Two Higgs Doublet Model of type II with emphasis on the possible existence of very light neutral (pseudo)scalar Higgs boson with mass below 20–30 GeV. We show that even in the presence of such light particles, the 2HDM(II) can describe the electroweak data with the precision comparable to that given by the SM. Particularly interesting lower limits on the mass of the lighter neutral CP-even scalar are obtained in the scenario with light CP-odd Higgs boson and large . Received: 8 June 1999 / Published online: 14 October 1999