122784266
Singularities of the space-time of plane domain wall when coupled with a scalar field
Abstract An exact solution of the Einstein-scalar field equations is given, which represents the Vilenkin planar domain wall coupled with a massless scalar field. It is found that, besides a big-bang singularity, the space-time has other curvature singularities, the proper distance from which to the wall is finite, and inversely proportional to the surface energy density of the wall.
119227824
Cosmological constant and late transient acceleration of the universe in the Horava-Witten Heterotic M-Theory on S^{1}/Z_{2}
Abstract Orbifold branes are studied in the framework of the 11-dimensional Horava–Witten heterotic M-theory. It is found that the effective cosmological constant can be easily lowered to its current observational value by the mechanism of large extra dimensions. The domination of this constant over the evolution of the universe is only temporary. Due to the interaction of the bulk and the branes, the universe will be in its decelerating expansion phase again in the future, whereby all problems connected with a far future de Sitter universe are resolved.
2444705
Gravitational and particle radiation from long cosmic strings
Gravitational and massless particle radiation from infinitely long cosmic strings with finite thickness is studied by constructing analytic solutions to the Einstein field equations with certain forms of energy - momentum tensor. Using Thorne's -energy arguments, it is shown that the radiation always carries away energy. As a result, the angle defect outside the string is less than that in the non-radiation case. Since the solutions are exact, the back reaction of the radiation is automatically taken into account. In fact, it is shown that because of this back reaction the spacetime is always singular on the symmetry axis. The singularity is a scalar one and not removable.
10393301
On the sources of static plane symmetric vacuum space-times
Abstract The sources of static vacuum plane space-times with reflection symmetry are considered. It is argued that the counterpart of the Einstein theory to the gravitational field of a massive Newtonian plane should be described by the Rindler solution, which represents also a uniform gravitational field, and the test particles moving in which have constant accelerations.
119168760
Homothetic self-similar solutions of three-dimensional Brans-Dicke gravity
All homothetic self-similar solutions of the Brans-Dicke scalar field in three-dimensional spacetime with circular symmetry are found in closed form.
109935503
No-Go theorem in spacetimes with two commuting spacelike killing vectors
Four-dimensional Riemannian spacetimes with two commuting spacelike Killing vectors are studied in Einstein's theory of gravity, and found that no outer apparent horizons exist, provided that the dominant energy condition holds.
117264492
Reply to Comment of Gazdzicki and Heinz on Strangeness Enhancement in $p+A$ and $S+A$
The Comment of Gazdzicki and Heinz is flawed because their assumed baryon stopping power in $pA$ is inconsistent with data and because they ignored half the analysis based on the VENUS model. The Comment continues the misleading presentation of strangeness enhancement by focusing on ratios of integrated yields. Those ratios discard essential experimental information on the rapidity dependence of produced $\Lambda$ and obscure discrepancies between different data sets. Our conclusion remains that the NA35 minimum bias data on $p+S\rightarrow\Lambda +X $ indicate an anomalous enhancement of central rapidity strangeness in few nucleon reactions that points to non-equilibrium dynamics as responsible for strangeness enhancement in nuclear reactions.
119819008
Large angle elastic and inelastic scattering of protons from Ca 40 at 800 MeV
Measurements are reported for the elastic and inelastic scattering of 800 MeV protons from $^{40}\mathrm{Ca}$. Differential cross sections were measured out to 42\ifmmode^\circ\else\textdegree\fi{} while analyzing powers were obtained out to 30\ifmmode^\circ\else\textdegree\fi{}. The angular distributions are diffractive in character at all angles. Theoretical analysis of the data was carried out in the framework of the diffraction multiple scattering theory. The following results were obtained: (i) Diffraction multiple scattering theory reproduces the data qualitatively out to the large momentum transfers. (ii) For the ground state density distribution ${〈{{r}_{p}}^{2}〉}^{\frac{1}{2}}\ensuremath{-}{〈{{r}_{n}}^{2}〉}^{\frac{1}{2}}=0.142\ifmmode\pm\else\textpm\fi{}0.075$ fm is obtained and the analysis favors the value of the correlation length ${\ensuremath{\xi}}_{c}=\ensuremath{-}0.5$ fm. (iii) The excitation of the lowest-lying collective states (${3}^{\ensuremath{-}}$, ${5}^{\ensuremath{-}}$, ${2}^{+}$) was analyzed using one-phonon excitation macroscopic parameters. The values of the ${\ensuremath{\beta}}_{2}$, ${\ensuremath{\beta}}_{3}$, ${\ensuremath{\beta}}_{5}$ parameters obtained agree quantitatively with lower energy ($p$,${p}^{\ensuremath{'}}$) scattering results.
81234
Levi-Civita solutions coupled with electromagnetic fields
The local and global properties of the Levi-Civita (LC) solutions coupled with an electromagnetic field are studied and some limits to the vacuum LC solutions are given, from which the physical and geometrical interpretations of the free parameters involved in the solutions are made clear. Sources for both the LC vacuum solutions and the LC solutions coupled with an electromagnetic field are studied, and in particular it is found that all the LC vacuum solutions with σ ≥ 0 can be produced by cylindrically symmetric thin shells that satisfy all the energy conditions, weak, dominant and strong. When the electromagnetic field is present, the situation changes dramatically. In the case of a purely magnetic field, all the solutions can be produced by physically acceptable cylindrical thin shells, while in the case of a purely electric field, no such shells are found for any choice of the free parameters involved in the solutions.
120198608
Differential cross sections and analyzing powers for pp elastic scattering at 1. 46 GeV/c in the Coulomb-nuclear interference region
Differential cross sections sigma(theta) and analyzing powers A(theta) for pp elastic scattering have been measured in the Coulomb-nuclear interference region at 800 MeV. The measurements, which extend down to 0.5 deg in the laboratory, have been analyzed to deduce the zero-degree pp scattering amplitudes. The ratio rho of the real to imaginary parts of the spin-independent amplitude was found to be -0.04 +- 0.04; the contribution of the double-spin-flip amplitudes to sigma(0) was found to be 0.16 +- 0.03 times that of the spin-independent amplitude; while the ratios of the imaginary and real parts of the single spin-flip amplitude to sintheta were found to be 0.74 +- 0.04 and -0.03 +- 0.08 fm, respectively. Except for the last, these experimental values agree with the predictions of forward dispersion relations and phase shift analyses.
123322377
PLANAR DOMAIN WALLS COUPLED WITH PURE RADIATION FIELDS
All the exact solutions of the Einstein-Maxwell-Weyl equations are given, which represent planar domain walls coupled with electromagnetic and neutrino radiation fields. Some specific solutions are studied.