Search results for "string [quantum chromodynamics]"
showing 10 items of 166 documents
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…
On the chirality of the SM and the fermion content of GUTs
2015
The Standard Model (SM) is a chiral theory, where right- and left-handed fermion fields transform differently under the gauge group. Extra fermions, if they do exist, need to be heavy otherwise they would have already been observed. With no complex mechanisms at work, such as confining interactions or extra-dimensions, this can only be achieved if every extra right-handed fermion comes paired with a left-handed one transforming in the same way under the Standard Model gauge group, otherwise the new states would only get a mass after electroweak symmetry breaking, which would necessarily be small (similar to 100 GeV). Such a simple requirement severely constrains the fermion content of Grand…
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.
Finite Quantum Gravity Amplitudes: No Strings Attached
2020
We study the gravity-mediated scattering of scalar fields based on a parameterisation of the Lorentzian quantum effective action. We demonstrate that the interplay of infinite towers of spin zero and spin two poles at imaginary squared momentum leads to scattering amplitudes that are compatible with unitarity bounds, causal, and scale-free at trans-Planckian energy. Our construction avoids introducing non-localities or the massive higher-spin particles that are characteristic in string theory.
Kaluza-Klein origin for the superstring tension
1992
The natural configuration space of a string in a background antisymmetric tensor potential is not loop space, but a principal U(1) bundle over loop space. This allows a Kaluza-Klein--like interpretation of the string tension as momentum along the U(1) fiber, and a similar interpretation is possible for a {ital p}-dimensional object. The higher-dimensional'' action incorporating this momentum as a dynamical variable is given for a {ital p}-dimensional supersymmetric extended object, in a general supergravity background. Its relevance, for a flat background, to classical anomalies'' in the supersymmetry algebra is explained.
Quasidisks and string theory
1990
Abstract A heuristic model of non-perturbative bosonic string theory on the Bers universal Teichmuller space of normalized quasidisks is discussed. It is suggested that the infinite-dimensional analogue of the Polyakov energy might be the quasidisk area.
Supersymmetry currents and WZ-like terms in (supersymmetry)2 models
1990
Abstract Using the superfield formulation of the N = 1 spinning superparticle model as an example, the superfield currents associated with the target space supersymmetry are given, and the component expression of the corresponding superalgebra is found to describe a graded “doubling” of the Poincare superalgebra. Further, it is shown how the torsion-like term in the spinning super-particle model can be obtained from the form associated with the Green-Schwarz WZ term for the superstring, and a possible way of introducing extended spinning supersymmetric objects is discussed.