abstract

In the framework of mean-field approximation the dynamics of Bose–Einstein condensates can be described by the hydrodynamic-like equations. These equations are analyzed here with account of mutual interaction between condensate and non-condensate atoms. The Lagrange invariants and freezing-in invariants of such a system have been found. This allows to get some necessary conditions for creation of an atom laser with controlled parameters of the beam. Particularly, the atom laser beam can carry quite well defined angular momentum. This can be practically realized in the most simple case, when the vorticity of condensate appears to be a freezing-in field. The optimal conditions for a source mode regime are found.

abstract

It is shown that the isomorphism between the generalized Moyal algebra and the matrix algebra follows in a natural manner from the generalized Weyl quantization rule and from the well known matrix representation of the annihilation and creation operators.

abstract

Using Bohm’s quantum mechanics, a wide class of related two-parameter dynamical systems is proposed and their general properties are briefly discussed, in particular, a possibility of chaotic solutions. When the systems are reduced to a one-parameter family of equations then they are all proved to be completely integrable and integrals of the motion are found in an explicite form. The proposed class of dynamical systems can be cast into the form of Hamiltonian equations forced by a time-dependent non-Hamiltonian, periodic in time, disturbance. A systematic way of generating dynamical systems of this kind is also discussed.

abstract

We present the general equations of motion for null and tensile strings in the Peres spacetime and give the general solutions in quadratures in the case of null strings. As for the tensile strings we integrate equations of motion and constraints completely in a closed form for circular and straight string Ansäts.

abstract

The nonmesonic decay of the \({\mit \Lambda }\)-hyperon has been investigated by observation of delayed fission of heavy hypernuclei produced in proton–U collisions at \(T_p=1.9\) GeV. The lifetime of heavy hypernuclei with masses \(A\!\approx \! 220\) obtained in the present work, i.e. \(\tau _{{\mit \Lambda }}\!=\! [138\! \pm \! 6 ({\rm stat.})\! \pm \! 17 ({\rm syst.})]\!\) ps, is the most accurate result for heavy hypernuclei produced in proton and antiproton induced collisions on a U target so far.

abstract

The sensitivity of THERA to different models of “new physics” has been studied, both for the contact interaction approximation and for the resonance production. For contact interaction models conserving parity, scales up to about 18 TeV can be explored at THERA, extending considerably beyond the existing bounds. Significant improvement of existing limits is also expected for models with large extra dimensions. Effective Plank mass scales up to about 2.8 TeV can be probed. THERA will be the best machine to study leptoquark properties, for leptoquark masses up to about 1 TeV. It will be sensitive to the leptoquark Yukawa couplings down to \(\lambda _{\rm LQ} \!\sim \! 10^{-2}\).

abstract

An effective texture is presented for six Majorana conventional neutrinos (three active and three sterile), based on a \(6\times 6\) neutrino mixing matrix whose \(3\times 3\) active–active component arises from the popular bimaximal mixing matrix of active neutrinos \( \nu _e\,, \,\nu _\mu \,, \,\nu _\tau \) by three small rotations in the 14, 25, 36 planes of \( \nu _1\,, \,\nu _2\,, \,\nu _3 \) and \( \nu _4\,, \,\nu _5\,, \,\nu _6 \) neutrino mass states. The Dirac component (i.e. , \(3\times 3\) active-sterile component) of the resulting \(6\times 6\) neutrino mass matrix is conjectured to get a structure similar to the charged-lepton and quark \(3\times 3\) mass matrices, after the bimaximal mixing, specific for neutrinos, is transformed out unitarily from the neutrino mass matrix. The charged-lepton and quark mass matrices are taken in a universal form constructed previously by the author with a conside- rable phenomenological success. Then, for the option of \( m^2_1 \simeq m^2_2 \simeq m^2_3 \gg m^2_4 \simeq m^2_5 \simeq m^2_6 \simeq 0\), the proposed texture predicts oscillations of solar \(\nu _e\)’s with \(\Delta m^2_{\rm sol} \equiv \Delta m^2_{21} \sim \,\) (1.1 to \(1.2) \times 10^{-5}\;{\rm eV}^2\), not inconsistent with the LMA solar solution, if the SuperKamiokande value \(\Delta m^2_{\rm atm} \equiv \Delta m^2_{32} \sim \,\) \((3\ {\rm to}\ 3.5)\times 10^{-3}\;{\rm eV}^2\) for oscillations of atmospheric \(\nu _\mu \)’s is taken as an input. Here, \(\sin ^2 2\theta _{\rm sol} \sim 1\) and \( \sin ^2 2 \theta _{\rm atm} \sim 1\). The texture predicts also an LSND effect with \(\sin ^2 2\theta _{\rm LSND}\sim \,\)(1.4 to \(1.9)\times 10^{-11}\,({\rm eV}/m_1)^4\) and \(\Delta m^2_{\rm LSND} \equiv \Delta m^2_{25} \sim m^2_1 + \,\)(1.1 to 1.2)\(\,\times 10^{-5}\;{\rm eV}^2\). Unfortunately, the Chooz experiment imposes on the LSND effect (in our texture) a very small upper bound \(\sin ^2 2\theta _{\rm LSND} \lesssim 1.3 \times 10^{-3}\), which corresponds to the lower limit \( m_1 \gtrsim \, \)(1.0 to \(1.1)\times 10^{-2}\,{\rm eV}\).

abstract

We show that in the dual version of the generalized Dick model monopole-anti-monopole pairs have finite energy. It is possible to use the potential between monopole and anti-monopole to find the mass spectrum of the glueballs. The results are discussed in connection with the Faddeev–Niemi model and toroidal soliton solutions. Some other finite energy configurations are found, both in the magnetic and electric sector.

abstract

The quantization conditions which come from the requirement of the singlevaluedness of the odderon wave function are formulated and solved numerically in the 4 dimensional space of the odderon charge \(q_3\) and the conformal weight \(h\). It turns out that these conditions are fulfilled along one dimensional curves parametrized by a discrete set of values of Re \(h\) in 3 dimensional subspace (Im\(~h\),Im\(~q_3\),Re\(~q_3)\). The odderon energy calculated along these curves corresponds in all cases to the intercept lower than 1.

abstract

We investigate the possibility that the process of \(\rho ^{0}\)-meson photoproduction on proton, \(\gamma +p\rightarrow p+\rho ^{0}\), in the near threshold region \(E_{\gamma }\lt 2\) GeV, can be considered in the framework of model with \(\pi \)-, \(\sigma \)- and \(N\)-exchanges. This suggestion is based on a study of the t-dependence of differential cross section, \(d\sigma (\gamma p \rightarrow p \rho ^{0})/dt\), which has been measured by SAPHIR Collaboration. We find that the suggested model provides a good description of the experimental data with new values of \(\rho NN\)-coupling constants in the region of the time-like \(\rho ^{0}\)-meson momentum. Our results suggest that such model can be considered as a suitable nonresonant background mechanism for the future discussion of possible role of nucleon resonance contributions. Our predictions for \(\rho ^{0}\)-meson photoproduction on neutron target and for beam asymmetry on both proton and neutron targets are presented.

abstract

The hadronic \(\tau \) decay of a heavy charged Higgs boson, \(H^\pm \rightarrow \tau \nu \), is considered in ATLAS. In the mass region \(m_{H^\pm } \gt m_t\), the most relevant decay channels of the charged Higgs boson are \(H^\pm \rightarrow tb\) and \(H^\pm \rightarrow \tau \nu \). Whereas the former suffers from large irreducible backgrounds, the latter offers a relatively clean environment with the appropriate cuts. In addition, a further suppression of the backgrounds is achieved by making use of the polarization of the \(\tau \) lepton.

abstract

Kaon-nucleus scattering has been analyzed using an equivalent local potential to calculate the differential elastic, total, and reaction cross sections from \(^{2}\)H, \(^{6}\)Li, \(^{12}\)C, \(^{28}\)Si, and \(^{40}\)Ca at kaon lab momenta ranging from 488 to 800 MeV/\(c\). The DWUCK4 computer program was used to predict observables of kaon–nucleus scattering. Our results are successfully compared to recent data.

abstract

The low-lying levels of \(^{93}\)Nb nucleus were excited with 2.7–4.3 MeV proton beam. The de-excited gamma-rays from this nucleus were identified in the singles spectra recorded with a 70 cm\(^{3}\) HpGe detector. The reduced quadrupole transition probabilities of the low-lying levels have been measured via coulomb excitation technique using safe bombarding energy of 3.5 MeV proton beam. The angular distributions have been used to assign the spin of 1082.9 keV level and obtained the multipole mixing ratios of the various transitions. The present results on \(B\)(E2) have been compared with the reported measurements and model calculations.

abstract

We study properties of the proton component of neutron star matter for a number of realistic nuclear models. Protons which form a few percent admixture tend to be localized in potential wells corresponding to neutron matter inhomogeneities created by the protons in the neutron medium. We calculate the energy of the Wigner–Seitz cell enclosing a single localized proton. The neutron background is treated in the Thomas–Fermi approximation and the localized proton is described by the Gaussian wave function. The neutron density profile is obtained by solving the appropriate variational equation. This approach gives lower energies of localized protons than obtained previously with less sophisticated methods.

abstract

The thermal model of particle production is used to analyze the par- ticle ratios and the \(p_\perp \) spectra measured recently at RHIC. Our fit of the particle ratios yields the temperature at the chemical freeze-out \(T_{\rm chem}\!= 165 \pm \)7 MeV with the corresponding baryon chemical potential \(\mu ^{\rm B}_{\rm chem}\!= 41 \pm 5\) MeV. The quality of the fit shows that the model works well for RHIC. The \(p_\perp \) spectra are evaluated in an approach which takes into account the modifications of the initial thermal distributions by the secondary decays of resonances. All two- and three-body decays are included. This leads to an effective “cooling” of the spectra in the data region by about 30–40 MeV. We find that the pion spectrum is characterized by the inverse slope which agrees well with the value inferred from the RHIC data.

abstract

Using Landau-de Gennes effective theory for nematic liquid crystals we analyse structure of a rectilinear, \(n=1/2\), smooth disclination line in the case of equal elastic constants. We find that at certain temperature there is an exact mathematical correspondence with a rectilinear vortex in superfluid \(^{4}\)He. With a help of polynomial approximation difference of free energies of smooth and singular disclination lines is estimated. It turns out that the smooth disclination line is energetically preferred only if temperature is low enough. At higher temperatures a disordered core should be expected.