A study of global monopole in Lyra geometry

A class of exact static solution around a global monopole resulting from the breaking of a global S0(3) symmetry is obtained in the context of Lyra geometry. Our solution is shown to possess an interesting feature like wormholes space-time. It has been shown that the global monopole exerts no gravitational force on surrounding non-relativistic matter.Comment: 6 pages, Published in Mod.Phys.Lett.A19:2785-2790,200

Poluklasični gravitacijski efekti blizu kozmičke strune u Lyrinoj geometriji

In recent past, W. A. Hiscock [Phys. Lett. B 188 (1987) 317] studied the semi-classical gravitational effects near cosmic strings. He obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal massless free-quantum fields (scalar, spinor and vectors) in the presence of a static, cylindrically symmetric cosmic string. With this stress-energy tensor, we study the semi-classical gravitational effects of a cosmic string in the context of Lyra geometry.Nedavno je W. A. Hiscock [Phys. Lett. B 188 (1987) 317] proučavao poluklasične gravitacijske efekte u blizini kozmičkih struna. Izveo je vakuumsku očekivanu vrijednost za tenzor naprezanja-energije za proizvoljan skup konformnih, bezmasenih i slobodnih kvantnih polja (skalara, spinora i vektora) u prisustvu statičke cilindrično-simetrične kozmičke strune. S tim tenzorom proučavamo poluklasične gravitacijske efekte kozmičke strune u okviru Lyrine geometrije

Proučavanje globalnih struna u Lyrinoj geometriji

An exact solution for the space-time outside the core of a U(1) static global string in Lyra geometry is presented. Our global string is nonsingular at a finite distance from the string core. The gravitational field of the global string is shown to be attractive in nature.Dajemo egzaktno rješenje za prostor-vrijeme izvan sredice mirne globalne U(1) strune u Lyrinoj geometriji. Nalazi se da globalna struna nije singularna na konačnoj daljini od sredice strune. Pokazuje se da je gravitacijsko polje globalne strune privlačno

Vacuumless topological defects in Lyra geometry

Few years ago, Cho and Vilenkin have proposed that topological defects can arise in symmetry breaking models without having degenerate vacua. These types of defects are known as vacuumless defects. In the present work, the gravitational field of a vacuumless global string and global monopole have been investigated in the context of Lyra geometry. We find the metric of the vacuumless global string and global monopole in the weak field approximations. It has been shown that the vacuumless global string can have repulsive whereas global monopole exerts attractive gravitational effects on a test particle. It is dissimilar to the case studied in general relativity.Comment: 14 pages, 9 figures. To appear in Astrophys.Space.Sc

Selective Loss of Wild-Type p16INK4a Expression in Human Nevi

4 page(s

Electronic structure, phase stability and chemical bonding in Th2_2Al and Th2_2AlH4_4

We present the results of theoretical investigation on the electronic structure, bonding nature and ground state properties of Th$_2$Al and Th$_2$AlH$_4$ using generalized-gradient-corrected first-principles full-potential density-functional calculations. Th$_2$AlH$_4$ has been reported to violate the "2 \AA rule" of H-H separation in hydrides. From our total energy as well as force-minimization calculations, we found a shortest H-H separation of 1.95 {\AA} in accordance with recent high resolution powder neutron diffraction experiments. When the Th$_2$Al matrix is hydrogenated, the volume expansion is highly anisotropic, which is quite opposite to other hydrides having the same crystal structure. The bonding nature of these materials are analyzed from the density of states, crystal-orbital Hamiltonian population and valence-charge-density analyses. Our calculation predicts different nature of bonding for the H atoms along $a$ and $c$. The strongest bonding in Th$_2$AlH$_4$ is between Th and H along $c$ which form dumb-bell shaped H-Th-H subunits. Due to this strong covalent interaction there is very small amount of electrons present between H atoms along $c$ which makes repulsive interaction between the H atoms smaller and this is the precise reason why the 2 {\AA} rule is violated. The large difference in the interatomic distances between the interstitial region where one can accommodate H in the $ac$ and $ab$ planes along with the strong covalent interaction between Th and H are the main reasons for highly anisotropic volume expansion on hydrogenation of Th$_2$Al.Comment: 14 pages, 9 figure

Wilson Expansion of QCD Propagators at Three Loops: Operators of Dimension Two and Three

In this paper we construct the Wilson short distance operator product expansion for the gluon, quark and ghost propagators in QCD, including operators of dimension two and three, namely, A^2, m^2, m A^2, \ovl{\psi} \psi and m^3. We compute analytically the coefficient functions of these operators at three loops for all three propagators in the general covariant gauge. Our results, taken in the Landau gauge, should help to improve the accuracy of extracting the vacuum expectation values of these operators from lattice simulation of the QCD propagators.Comment: 20 pages, no figure