arXiv subjects
Publications and source records attributed to S. T. Love.
Transition probabilities for a class of two level systems described by explicitly time dependent Hamiltonians are considered. Provided only that the approach to the infinite time limit is non-trivial falling at least as fast as 1/t for large t, the transition probability takes a particularly simple form depending only on the value of Hamiltonian parameters in this limit.
Techni-fermions are added as stacks of D7-anti-D7 techni-branes within the framework of a holographic technicolor model that has been proposed as a realization of walking technicolor. The stability of the embedding of these branes is determined. When a sufficiently low bulk cut-off is provided the fluctuations remain small. For a longer walking region, as would be required in any realistic model of electroweak symmetry breaking, a larger bulk cut-off is needed and in this case the oscillations destabilize.
The relationship between local Weyl scaling invariant models and local dilatation invariant actions is critically scrutinized. While actions invariant under local Weyl scalings can be constructed in a straightforward manner, actions invariant under local dilatation transformations can only be achieved in a very restrictive case. The invariant couplings of matter fields to an Abelian vector field carrying a non-trivial scaling weight can be easily built, but an invariant Abelian vector kinetic term can only be realized when the local scale symmetry is spontaneously broken.
The minimal supersymmetric standard model (MSSM) is extended by including an additional pair of constrained Higgs doublet superfields through which the electroweak symmetry is nonlinearly realized. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze the later nontrivial vacuum expectation values. The mass spectrum of the Higgs scalars and Higgsino-gaugino sector is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The effect of the the additional constrained fields and multiple vacuum expectation values on the lowest mass neutral Higgs scalar production and decay is presented.
The electroweak symmetry is nonlinearly realized in an extension of the minimal supersymmetric standard model (MSSM) through an additional pair of constrained Higgs doublet superfields. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze their vacuum expectation values. The Higgs and Higgsino-gaugino mass spectrum is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The additional vacuum expectation values provided by the constrained fields can produce a phenomenology quite different than that of the MSSM .
Holographic currents and their associated Ward identities are derived in the framework of gravity/gauge duality. Holographic improvements of the energy-momentum tensor and R-symmetry current which are consistent with the Ward identities are displayed. The effects of specific string loop corrections to the bulk action are included as four derivative effective lagrangian terms and their contributions to the trace and R-symmetry anomalies of the boundary theory are determined. As an example, the construction is applied to the N=2 conformal supergravity which is taken to be dual to a boundary SU(N)xSU(N), N=1 superconformal field theory.
A minimal candidate for dark matter is provided by a stable standard model singlet hermitian scalar field. The quantum mechanical effects of this singlet are explored in a model where the standard model Higgs boson has a large non-minimal coupling to the Ricci scalar and plays the role of the inflaton. Imposition of the slow roll inflation cosmological constraints restricts the allowed values of the Higgs boson mass, its coupling to the dark matter and the dark matter self-coupling.
The standard model Higgs boson can serve as the inflaton field of slow roll inflationary models provided it exhibits a large non-minimal coupling with the gravitational scalar curvature. The Higgs boson self interactions and its couplings with a standard model singlet scalar serving as the source of dark matter are then subject to cosmological constraints. These bounds, which can be more stringent than those arising from vacuum stability and perturbative triviality alone, still allow values for the Higgs boson mass which should be accessible at the LHC. As the Higgs boson coupling to the dark matter strengthens, lower values of the Higgs boson mass consistent with the cosmological data are allowed.
Brane world oscillations manifest themselves as massive vector gauge fields. Their coupling to the Standard Model is deduced using the method of nonlinear realizations of the spontaneously broken higher dimensional space-time symmetries. Brane vectors are stable and weakly interacting, and therefore escape particle detectors unnoticed. LEP and Tevatron data on the production of a single photon in conjunction with missing energy are used to delineate experimentally excluded regions of brane vector parameter space. The additional region of parameter space accessible to the LHC as well as a future lepton linear collider is also determined by means of this process.
A Kaluza-Klein decomposition of higher dimensional gravity is performed in the flexible brane world scenario and the properties of the extra vectors resulting from this decomposition are explored. These vectors become massive due to a gravitational Higgs mechanism in which the brane oscillation Nambu-Goldstone bosons become the longitudinal component of the vector fields. The vector mass is found to be proportional to the exponential of the vacuum expectation value of the radion (dilaton) field and as such its magnitude is model dependent. Using the structure of the embedding geometry, the couplings of these vectors to the Standard Model, including those resulting from the extrinsic curvature, are deduced. As an example, we show that for 5D space-time the geometry of the bulk-brane world, either intrinsic or extrinsic, only depends on the extra vector and the 4D graviton. The connection between the embedding geometry and coset construction by non-linear realization is also presented.
Higgs boson decays in flexible brane world models with stable, massive gravi-vectors are considered. Such vectors couple bilinearly to the Standard Model fields through either the Standard Model energy-momentum tensor, the weak hypercharge field strength or the Higgs scalar. The role of the coupling involving the extrinsic curvature is highlighted. It is found that within the presently allowed parameter space, the decay rate of the Higgs into two gravi-vectors (which would appear as an invisible Higgs decay) can be comparable to the rate for any of the Standard Model decay modes.
Local oscillations of the brane world are manifested as masssive vector fields. Their coupling to the Standard Model can be obtained using the method of nonlinear realizations of the spontaneously broken higher dimensional space-time symmetries, and to an extent, are model independent. Phenomenological limits on these vector field parameters are obtained using LEP collider data and dark matter constraints.
Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the Poincare symmetries of D dimensional space-time due to the embedding of a p-brane with codimension N=D-p-1. The resulting world volume action is an ISO(1,p+N) invariant generalization of the Nambu-Goto action in d=p+1 dimensional space-time. Analogous results are obtained for an AdS p-brane with codimension N embedded in D dimensional AdS space, yielding an SO(2,p+N) invariant version of the Nambu-Goto action in d=p+1 dimensional space-time. Attention is focused on a supersymmetric extension of the D=6 Minkowski space case with an embedded p=3 brane; a particular realization of which is provided by a non-BPS vortex. Here both the Nambu-Goto-Akulov-Volkov action and its dual tensor form are presented.
Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the local Poincare symmetries of D dimensional space-time due to the embedding of a p-brane with codimension N=D-p-1. The resulting action is an ISO(1,p+N) invariant form of the Einstein-Hilbert action, which, in addition to the gravitational vielbein, also includes N massive gauge fields corresponding to the broken space translation symmetries which together carry the fundamental representation of the unbroken SO(N) gauge symmetry and an SO(N) Yang-Mills field localized on the brane. The long wavelength dynamics of the gravitating p-brane is the same as the action of an SO(N) vector massive Proca field and a non-Abelian SO(N) Yang-Mills field all coupled to gravity in d=(1+p) dimensional space-time. The general results are specialized to determine the effective action for the gravitating vortex solution in the D=6 Abelian Higgs-Kibble model.
Actions governing the dynamics of the Nambu-Goldstone modes resulting from the spontaneous breaking of the SO(4,2) and $SU(2,2|1)$ isometries of five dimensional anti-de Sitter space ($AdS_{5}$) and SUSY $AdS_{5}\times S_1$ spaces respectively due to a restriction of the motion to embedded four dimensional $AdS_{4}$ space and four dimensional Minkowski space ($M_4$) probe branes are presented. The dilatonic Nambu-Goldstone mode governing the motion of the $M_4$ space probe brane into the covolume of the SUSY $AdS_5\times S_1$ space is found to be unstable. No such instablility appears in the other cases. Gauging these symmetries leads to an Einstein-Hilbert action containing, in addition to the gravitational vierbein, a massive Abelian vector field coupled to gravity.
Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the local supersymmetries. The resulting action is an invariant form of the Einstein-Hilbert action, which in addition to the gravitational vierbein, also includes a massive gravitino field. Invariant interactions with matter and gauge fields are also constructed. The effective Lagrangian describing processes involving the emission or absorption of a single light gravitino is analyzed.
The isometries of $AdS_5$ space and supersymmetric $AdS_5\otimes S_1$ space are nonlinearly realized on four dimensional Minkowski space. The resultant effective actions in terms of the Nambu-Goldstone modes are constructed. The dilatonic mode governing the motion of the Minkowski space probe brane into the covolume of supersymmetric $AdS_5$ space is found to be unstable and the bulk of the $AdS_5$ space is unable to sustain the brane. No such instablility appears in the non-supersymmetric case.
Simultaneous nonlinear realizations of spontaneously broken supersymmetry in conjunction with other spontaneous and/or explicitly broken symmetries including R symmetry, global chiral symmetry, dilatations and the superconformal symmetries is reviewed.