Search results for "String Theory"
showing 10 items of 75 documents
Bose-Fermi equivalence and interacting string field theory
1995
Abstract We show that the bosonic and the fermionic realization of the ghost vertex in the Half-String (HS) Operator approach to Witten's String Field Theory (WSFT) are equivalent. In the process we discover that higher vertices (i.e., N > 3) can be eliminated in WSFT using only the overlap conditions defining the interaction vertex and ghost number counting.
The unitary conformal field theory behind 2D Asymptotic Safety
2015
Being interested in the compatibility of Asymptotic Safety with Hilbert space positivity (unitarity), we consider a local truncation of the functional RG flow which describes quantum gravity in $d>2$ dimensions and construct its limit of exactly two dimensions. We find that in this limit the flow displays a nontrivial fixed point whose effective average action is a non-local functional of the metric. Its pure gravity sector is shown to correspond to a unitary conformal field theory with positive central charge $c=25$. Representing the fixed point CFT by a Liouville theory in the conformal gauge, we investigate its general properties and their implications for the Asymptotic Safety progra…
Decoherence induced CPT violation and entangled neutral mesons
2006
We discuss two classes of semi-microscopic theoretical models of stochastic space-time foam in quantum gravity and the associated effects on entangled states of neutral mesons, signalling an intrinsic breakdown of CPT invariance. One class of models deals with a specific model of foam, initially constructed in the context of non-critical (Liouville) string theory, but viewed here in the more general context of effective quantum-gravity models. The relevant Hamiltonian perturbation, describing the interaction of the meson with the foam medium, consists of off-diagonal stochastic metric fluctuations, connecting distinct mass eigenstates (or the appropriate generalisation thereof in the case o…
Black hole solutions of N=2, d=4 supergravity with a quantum correction, in the H-FGK formalism
2012
We apply the H-FGK formalism to the study of some properties of a general class of black holes in N = 2 supergravity in four dimensions that correspond to the harmonic and hyperbolic ansatze and we obtain explicit extremal and non-extremal solutions for the t(3) model with and without a quantum correction. Not all solutions of the corrected model (quantum black holes), including in particular a solution with a single q(1) charge, have a regular classical limit.
The transverse structure of the QCD string
2010
The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is the appropriate probe to use when comparing with the nex…
Super Heavy Dark Matter Anisotropies from D-particles in the Early Universe
2004
We discuss a way of producing anisotropies in the spectrum of superheavy Dark matter, which are due to the distortion of the inflationary space time induced by the recoil of D-particles upon their scattering with ordinary string matter in the Early Universe. We calculate such distortions by world-sheet Liouville string theory (perturbative) methods. The resulting anisotropies are found to be proportional to the average recoil velocity and density of the D-particles. In our analysis we employ a regulated version of de Sitter space, allowing for graceful exit from inflation. This guarantees the asymptotic flatness of the space time, as required for a consistent interpretation, within an effec…
D=4 supergravity dynamically coupled to superstring in a superfield Lagrangian approach
2003
We elaborate a full superfield description of the interacting system of dynamical D=4, N=1 supergravity and dynamical superstring. As far as minimal formulation of the simple supergravity is used, such a system should contain as well the tensor (real linear) multiplet which describes the dilaton and the two-superform gauge field whose pull-back provides the Wess-Zumino term for the superstring. The superfield action is given by the sum of the Wess-Zumino action for D=4, N=1 superfield supergravity, the superfield action for the tensor multiplet in curved superspace and the Green-Schwarz superstring action. The latter includes the coupling to the tensor multiplet both in the Nambu-Goto and i…
Gauged extended supergravity without cosmological constant: No-scale structure and supersymmetry breaking
2002
We consider the interplay of duality symmetries and gauged isometries of supergravity models giving N-extended, spontaneously broken supergravity with a no-scale structure. Some examples, motivated by superstring and M-theory compactifications are described.
Superembedding Approach and S-Duality. A unified description of superstring and super-D1-brane
2001
It is proved that a basic superembedding equation for the 2-dimensional worldsheet superspace $\S^{(2|8+8)}$ embedded into D=10 type IIB superspace $M^{(10|16+16)}$ provides a universal, S-duality invariant description of a fundamental superstring and super-D1-brane. We work out generalized action principle, obtain superfield equations of motion for both these objects and find how the S-duality transformations relate the superfield equations of superstring and super-D1-brane. The superembedding of 6-dimensional worldsheet superspace $\S^{(6|16)}$ into the D=10 type IIB superspace will probably provide a similar universal description for the set of type IIB super-NS5-brane, super-D5-brane an…
First-order flows and stabilisation equations for non-BPS extremal black holes
2011
28 páginas.-- This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.