J. Mourad - Academia.edu (original) (raw)
Papers by J. Mourad
Journal of High Energy Physics, 2021
We investigate the effects of the leading tadpole potentials of 10D tachyon-free non-supersymmetr... more We investigate the effects of the leading tadpole potentials of 10D tachyon-free non-supersymmetric strings in warped products of flat geometries of the typeMp+1× R × T10−p−2depending on a single coordinate. In the absence of fluxes and forp <8, there are two families of these vacua for the orientifold disk-level potential, both involving a finite internal interval. Their asymptotics are surprisingly captured by tadpole-free solutions, isotropic for one family and anisotropic at one end for the other. In contrast, for the heterotic torus-level potential there are four types of vacua. Their asymptotics are always tadpole-dependent and isotropic at one end lying at a finite distance, while at the other end, which can lie at a finite or infinite distance, they can be tadpole-dependent isotropic or tadpole-free anisotropic. We then elaborate on the general setup for including symmetric fluxes, and present the three families of exact solutions that emerge when the orientifold potentia...
Letters in High Energy Physics, 2021
Journal of High Energy Physics, 2019
We study the perturbative stability of four settings that arise in String Theory, when dilaton po... more We study the perturbative stability of four settings that arise in String Theory, when dilaton potentials accompany the breaking of Supersymmetry, in the tachyon-free USp(32) and U(32) orientifold models, and also in the heterotic SO(16) × SO(16) model. The first two settings are a family ofAdS3×S7vacua of the orientifold models and a family ofAdS7×S3vacua of the heterotic model, supported by form fluxes, with small world-sheet and string-loop corrections within wide ranges of parameters. In both cases we find some unstable scalar perturbations, as a result of mixings induced by fluxes, confirming for the first class of vacua a previous result. However, in the second class of vacua they only affect theℓ= 1 modes, so that a ℤ2projection induced by an overall parity in the internal space suffices to eliminate them, leading to perturbative stability. Moreover, the constant dilaton profiles of these vacua allow one to extend the analysis to generic potentials, thus exploring the possibl...
A geometrical construction of superconformal transformations in six dimensional (2,0) superspace ... more A geometrical construction of superconformal transformations in six dimensional (2,0) superspace is proposed. Superconformal Killing vectors are determined. It is shown that the transformation of the tensor multiplet involves a zero curvature non-trivial cochain.
Journal of High Energy Physics, 2006
Letters in Mathematical Physics, 1995
Journal of Cosmology and Astroparticle Physics, 2004
International Journal of Theoretical Physics, 2005
Journal of Mathematical Physics, 1995
A modification of Kaluza–Klein theory is proposed which is general enough to admit an arbitrary f... more A modification of Kaluza–Klein theory is proposed which is general enough to admit an arbitrary finite noncommutative internal geometry. It is shown that the existence of a nontrivial extension to the total geometry of a linear connection on space–time places severe restrictions on the structure of the noncommutative factor. A counter-example is given.
International Journal of Modern Physics D, 1994
The commutative algebra of functions on a manifold is extended to a noncommutative algebra by con... more The commutative algebra of functions on a manifold is extended to a noncommutative algebra by considering its tensor product with the algebra of n×n complex matrices. Noncommutative geometry is used to formulate an extension of the Einstein-Hilbert action. The result is shown to be equivalent to the usual Kaluza-Klein theory with the manifold SUn as an internal space, in a truncated approximation.
AIP Conference Proceedings, 2006
A classical action is proposed which upon quantisation yields massless particles belonging to the... more A classical action is proposed which upon quantisation yields massless particles belonging to the continuous spin representation of the Poincar\'e group. The string generalisation of the action is identical to the tensionless extrinsic curvature action proposed by Savvidy. We show that the BRST quantisation of the string action gives a critical dimension of 28. The constraints result in a number of degrees of freedom which is the same as the bosonic string.
Journal of High Energy Physics, 2006
We study the consequences of twisting the coalgebra structure of Poincare group in a quantum fiel... more We study the consequences of twisting the coalgebra structure of Poincare group in a quantum field theory on a flat space-time. First, we construct a tensor product representation space compatible with the twisting and the corresponding creation and annihilation operators. Then, we show that a covariant field linear in creation and annihilation operators does not exist. Relaxing the linearity condition, a covariant field can be determined. We show that it is related to the untwisted field by a unitary transformation and the resulting n-point functions coincide with the untwisted ones. We also show that invariance under the twisted symmetry can be realized using the covariant field with the usual product or by a non-covariant field with a Moyal product. The resulting S-matrix elements are shown to coincide with the untwisted ones up to a momenta dependent phase.
Journal of High Energy Physics, 2021
We investigate the effects of the leading tadpole potentials of 10D tachyon-free non-supersymmetr... more We investigate the effects of the leading tadpole potentials of 10D tachyon-free non-supersymmetric strings in warped products of flat geometries of the typeMp+1× R × T10−p−2depending on a single coordinate. In the absence of fluxes and forp <8, there are two families of these vacua for the orientifold disk-level potential, both involving a finite internal interval. Their asymptotics are surprisingly captured by tadpole-free solutions, isotropic for one family and anisotropic at one end for the other. In contrast, for the heterotic torus-level potential there are four types of vacua. Their asymptotics are always tadpole-dependent and isotropic at one end lying at a finite distance, while at the other end, which can lie at a finite or infinite distance, they can be tadpole-dependent isotropic or tadpole-free anisotropic. We then elaborate on the general setup for including symmetric fluxes, and present the three families of exact solutions that emerge when the orientifold potentia...
Letters in High Energy Physics, 2021
Journal of High Energy Physics, 2019
We study the perturbative stability of four settings that arise in String Theory, when dilaton po... more We study the perturbative stability of four settings that arise in String Theory, when dilaton potentials accompany the breaking of Supersymmetry, in the tachyon-free USp(32) and U(32) orientifold models, and also in the heterotic SO(16) × SO(16) model. The first two settings are a family ofAdS3×S7vacua of the orientifold models and a family ofAdS7×S3vacua of the heterotic model, supported by form fluxes, with small world-sheet and string-loop corrections within wide ranges of parameters. In both cases we find some unstable scalar perturbations, as a result of mixings induced by fluxes, confirming for the first class of vacua a previous result. However, in the second class of vacua they only affect theℓ= 1 modes, so that a ℤ2projection induced by an overall parity in the internal space suffices to eliminate them, leading to perturbative stability. Moreover, the constant dilaton profiles of these vacua allow one to extend the analysis to generic potentials, thus exploring the possibl...
A geometrical construction of superconformal transformations in six dimensional (2,0) superspace ... more A geometrical construction of superconformal transformations in six dimensional (2,0) superspace is proposed. Superconformal Killing vectors are determined. It is shown that the transformation of the tensor multiplet involves a zero curvature non-trivial cochain.
Journal of High Energy Physics, 2006
Letters in Mathematical Physics, 1995
Journal of Cosmology and Astroparticle Physics, 2004
International Journal of Theoretical Physics, 2005
Journal of Mathematical Physics, 1995
A modification of Kaluza–Klein theory is proposed which is general enough to admit an arbitrary f... more A modification of Kaluza–Klein theory is proposed which is general enough to admit an arbitrary finite noncommutative internal geometry. It is shown that the existence of a nontrivial extension to the total geometry of a linear connection on space–time places severe restrictions on the structure of the noncommutative factor. A counter-example is given.
International Journal of Modern Physics D, 1994
The commutative algebra of functions on a manifold is extended to a noncommutative algebra by con... more The commutative algebra of functions on a manifold is extended to a noncommutative algebra by considering its tensor product with the algebra of n×n complex matrices. Noncommutative geometry is used to formulate an extension of the Einstein-Hilbert action. The result is shown to be equivalent to the usual Kaluza-Klein theory with the manifold SUn as an internal space, in a truncated approximation.
AIP Conference Proceedings, 2006
A classical action is proposed which upon quantisation yields massless particles belonging to the... more A classical action is proposed which upon quantisation yields massless particles belonging to the continuous spin representation of the Poincar\'e group. The string generalisation of the action is identical to the tensionless extrinsic curvature action proposed by Savvidy. We show that the BRST quantisation of the string action gives a critical dimension of 28. The constraints result in a number of degrees of freedom which is the same as the bosonic string.
Journal of High Energy Physics, 2006
We study the consequences of twisting the coalgebra structure of Poincare group in a quantum fiel... more We study the consequences of twisting the coalgebra structure of Poincare group in a quantum field theory on a flat space-time. First, we construct a tensor product representation space compatible with the twisting and the corresponding creation and annihilation operators. Then, we show that a covariant field linear in creation and annihilation operators does not exist. Relaxing the linearity condition, a covariant field can be determined. We show that it is related to the untwisted field by a unitary transformation and the resulting n-point functions coincide with the untwisted ones. We also show that invariance under the twisted symmetry can be realized using the covariant field with the usual product or by a non-covariant field with a Moyal product. The resulting S-matrix elements are shown to coincide with the untwisted ones up to a momenta dependent phase.