Necessary conditions for having wormholes in f(R) gravity

Dynamical Wormholes and Energy Conditions

A class of exact solutions of the Einstein field equations representing non-static wormholes that obey the weak and dominant energy conditions is presented. Hence, in principle, these wormholes can be built with less exotic matter than the static ones. PACS numbers: 04.20.Jb, 04.20.Cv, 04.60.+n, 03.70.+k e-mail address: [email protected] e-mail address: [email protected] 1 The idea of wormholes ...

Geometric Dilaton Gravity and Smooth Charged Wormholes *

A particular type of coupling of the dilaton field to the metric is shown to admit a simple geometric interpretation in terms of a volume element density independent from the metric. For dimension n = 4 two families of either magnetically or electrically charged static spherically symmetric solutions to the Maxwell–Einstein–Dilaton field equations are derived. Whereas the metrics of the “magnet...

Some Results on Necessary Conditions for Tow Quasidifferentiable Optimization Problems

New Necessary Conditions for

In this paper, we obtain several nonexistence results for abelian Hadamard diier-ence sets. In particular, we prove that there are no Hadamard diierence sets in abelian groups G = Z 2 Z 2 P , where jPj = p 2 , is odd and p is a prime congruent to 1(mod 4). Also we give a detailed proof for a connection between certain reversible Hadamard diierence sets and projective three-weight codes which wa...

Ellipsoidal, Cylindrical, Bipolar and Toroidal Wormholes in 5D Gravity

In this paper we construct and analyze new classes of wormhole and flux tube-like solutions for the 5D vacuum Einstein equations. These 5D solutions possess generic local anisotropy which gives rise to a gravitational running or scaling of the Kaluza-Klein “electric” and “magnetic” charges of these solutions. It is also shown that it is possible to self–consistently construct these anisotropic ...