39568649
Evolution of the density parameter in multidimensional cosmology.
Inflation as a dynamical effect of extra dimensions is discussed from the viewpoint of the evolution of the parameters Ω and q in the physical space. By reducing the dynamics of the models FLRW (k=±1)×T D (T D =S 1 ×... ×S 1 ) and FLRW (k=0)×S D , where FLRW denotes Friedmann, Lemaitre, Robertson, and Walker, to two dimensions it is shown that inflation need not imply Ω≃ 1 for the present time, i.e., that it does not solve the flatness problem. The energy-momentum tensor of the form T υ μ =(ρ,mρ,mρ,mρ,nρ,..., nρ) is assumed
120228178
On dynamical dimensional reduction
Abstract A mechanism is discussed of the dynamical dimensional reduction in the model B(I)×B(IX), where B(I) and B(IX) denote Bianchi I and Bianchi IX models respectively, in approximation of small anisotropies: the space with the isotropic internal sector is not reached monotonically, but exhibits oscillations around the isotropic state.
122597871
Differential structure of space-time and its prolongations to singular boundaries
After briefly presenting basic ideas of the differential space theory, the global description of space-times in terms of this theory is given. The space-times of a straight cosmic string and that of the closed Friedman world model are our standard examples. A space-time with its singular boundary is no longer a differentiable manifold, but it can be organized into a differential space, and the differential structure of space-time can be prolonged to its singular boundary. In general, the procedure is not unique. A simple classification of differential structure prolongations is also presented.
123580532
Kantowski-Sachs multidimensional cosmological models and dynamical dimensional reduction
Einstein's field equations are solved for a multidimensional spacetime (KS)*Tm, where (KS) is a four-dimensional Kantowski-Sachs' spacetime (1966) and Tm is an m-dimensional torus. Among all possible vacuum solutions there is a large class of spacetimes in which the macroscopic space expands and the microscopic space contracts to a finite volume. The authors also consider a non-vacuum case and they explicitly solve the field equations for the matter satisfying the Zel'dovich equations of state (1987). In non-vacuum models, with matter satisfying an equation of state rho = gamma rho . O<or= gamma rho (1, at a sufficiently late stage of evolution the microspace always expands and the dynamical dimensional reduction does not occur. Models (KS)*B(IX)*S1*S1*S1*S1 and (KS)*B(IX)*B(IX)*S1, where B(IX) is the Bianchi type-IX space, are also briefly discussed. It is shown that there is no chaotic behaviour in these cases. The same conclusion is also valid when one-loop high-temperature quantum corrections generated by a massless scalar field are taken into account.
120327098
Generic and nongeneric world models
Catastrophe theory methods are employed to obtain a new classification of those world models which can be presented in the form of gradient dynamical systems. Generic sets and structural stability of models in the potential space are strictly defined. It is shown that if a cosmological model is required to be Friedman and generic, it must be flat.
15464348
TOWARDS NONCOMMUTATIVE QUANTIZATION OF GRAVITY
We propose a mathematical structure, based on a noncommutative geometry, which combines essential aspects of general relativity with those of quantum mechanics, and leads to correct “limiting cases” of both these physical theories. We (algebraically) quantize a groupoid constructed on space-time rather than space-time itself. Both space and time emerge in the transition process to the commutative case. Our approach clearly suggests that quantum gravitational observables should be looked for among correlations of distant phenomena rather than among local effects. A toy model is computed (based on a finite group) which predicts the value of “cosmological constants” (in the quantum sector) which vanish when going to the standard space-time physics.
32857126
Polarization of Xi - and Omega - hyperons produced from neutral beams.
19721612
Evidence for muon production by particles from Cygnus X-3.
We have observed underground cosmic-ray muons, corresponding to a secondary flux of approx.7 x 10/sup -11/ cm/sup -2/ s/sup -1/, at a depth of 1800-m water equivalent, which appear to be initiated by Cygnus X-3. This identification is based on both direction and phase coherence. The existence of such secondary muons conflicts with the current understanding of photon cascades and/or the nature and location of Cygnus X-3.
39491989
Observation of the Meissner effect in a lattice Higgs model.
The lattice-regularized U(1) Higgs model in an external electromagnetic field is studied by Monte Carlo techniques. In the Coulomb phase magnetic flux can flow through uniformly. The Higgs phase splits into a region where magnetic flux can penetrate only in the form of vortices and a region where the magnetic flux is completely expelled, the relativistic analog of the Meissner effect in superconductivity. We present evidence for symmetry restoration in strong external fields.
42339487
B spectroscopy from NRQCD with dynamical fermions.
We present a lattice investigation, partially including the effects of dynamical quarks, of the heavy-light mesons using NRQCD for the heavy quark and the Wilson action for the light quark. We perform an extensive calculation of the spectrum employing a multistate, multiexponential fitting analysis which enables us to extract the 2{ital S}-1{ital S} splitting as well as the {sup 1}{ital P}{sub 1}-{ital {bar S}} and hyperfine splittings. The Wilson action introduces a large systematic error into the calculation, and within this uncertainty we obtain agreement with experiment. We perform a comprehensive calculation of the heavy-light meson mass, investigating three methods and their range of validity. The agreement found between these methods confirms that Lorentz invariance can be restored at this order in NRQCD by a constant shift to all masses. We calculated spectroscopic quantities over a wide range in heavy quark mass and are able to perform a detailed investigation of heavy quark symmetry around the {ital b} quark mass. In particular, we extract the nonperturbative coefficients of terms in the heavy quark expansion of the meson binding energy. We demonstrate the importance of using tadpole-improved operators in such a calculation. {copyright} {ital 1996 The American Physical Society.}
44737686
Hadron spectrum and matrix elements in QCD with dynamical Wilson fermions at 6/g2=5.3.
We present results of a lattice simulation of quantum chromodynamics with two degenerate flavors of dynamic Wilson fermions at $\frac{6}{{g}^{2}}=5.3$ at each of two dynamical fermion hopping parameters $\ensuremath{\kappa}=0.1670 \mathrm{and} 0.1675$ corresponding to pion masses in lattice units of about 0.45 and 0.31. The simulations include three other values of valence quark mass, in addition to the dynamical quarks. We present calculations of masses and of the decay constants of vector mesons and of pseudoscalars, including the $D$-meson decay constant. The effects of sea quarks on matrix elements and spectroscopy are small.