Use of compensators to break supersymmetry in an N = 1 supergravity theory

We consider an N = 1 supergravity theory with multiple compensators and show that supersymmetry is broken by a solution to the equation of motion of a compensator. When a chiral scalar superfield is coupled to supergravity, we discuss various aspects of supersymmetry breaking and show that the super-Higgs-Kibble effect is operative. Possible applications of this mechanism of supersymmetry breaking in model building and extended supergravity theories are indicated.     

Grand unification with local supersymmetry

We study general conditions for obtaining spontaneous breaking of local supersymmetry in N = 1 supergravity coupled to supersymmetric matter. We consider in particular the coupling of N = 1 supergravity to grand unified theories like SU(5) and study the conditions which must be met in order to obtain a realistic model. Specific models are built in which local supersymmetry is broken at a scale √M_Wm_p ～ 10¹⁰ GeV. This breaking of supersymmetry is only detected at low energies through soft terms breaking explicitly the global supersymmetry. These soft terms (scalar masses, gaugino masses and trilinear scalar couplings) are renormalized at low energies according to the renormalization group. The (mass)² of the Higgs doublet evolve towards negative values at low energies giving rise to SU(2) × U(1) breaking as a radiative effect of local supersymmetry breaking. We finally point out the possible relevance of non-renormalizable superpotentials for the problem of fermion masses.     

Spontaneous supersymmetry breaking by large-N matrices

Motivated by supersymmetry breaking in matrix model formulations of superstrings, we present some concrete models, in which the supersymmetry is preserved for any finite N, but gets broken at infinite N, where N is the rank of matrix variables. The models are defined as supersymmetric field theories coupled to some matrix models, and in the induced action obtained after integrating out the matrices, supersymmetry is spontaneously broken only when N is infinity. In our models, the large value of N gives a natural explanation for the origin of small parameters appearing in the field theories which trigger the supersymmetry breaking.     

Dynamical breakdown of supersymmetry and chiral symmetry in 1+1 dimensions

Dynamical breakdown of supersymmetry and chiral symmetry is studied through a 1+1 dimensional field theoretical model in the large-N limit in 1/N expansion. The study is based on the calculation of bilinear field condensates in an effective potential approach. It is shown that the condition for supersymmetry breaking is related to the values of the parameters in the model and chiral symmetry breaking exists in most cases.     

Spontaneous breaking of supersymmetry and gauge invariance in supergravity

Using the new minimal auxiliary fields of N = 1 supergravity it is found possible to construct a model of local supersymmetry which spontaneously breaks both supersymmetry and gauge invariance. The status of the cosmological constant resulting from this breaking is discussed.     

Primordial cosmological inflation versus local supersymmetry breaking in SUSY GUTs coupled toN=1 supergravity

We present a model for a SUSY GUT coupled toN=1 supergravity in which local supersymmetry breaks down in the gauge singlet sector. The constraints for the model to be physically acceptable are incompatible with inflation. The simultaneous breaking of local supersymmetry and gauge symmetry is proposed as a good prospect for inflation.     

Finiteness, 1/N expansion and supersymmetry breaking

The possibility of spontaneous supersymmetry breaking in the limit of large N, in models with an internal O(N) symmetry, is demonstrated by constructing an explicit example in two dimensions. The model is finite and this is shown to be important for the supersymmetry breaking. A general criterion for finiteness of scalar superfield theories in two dimensions is given. Finally, the generalization of our results to three dimensions, and their relevance to four-dimensional models, is discussed.     

Can inflation induce supersymmetry breaking in a metastable vacuum?

We argue that fields responsible for inflation and supersymmetry breaking are connected by gravitational couplings. In view of the recent progress in studying supersymmetry breaking in a metastable vacuum, we have shown that in models of supersymmetric hybrid inflation, where R-symmetry plays an important role, the scale of supersymmetry breaking is generated dynamically at the end of inflation and turns out to be consistent with gravity mediation.     

Supersymmetric flavon-chromon models

Using the supersymmetry and R-breaking mechanism induced by N=1 supergravity, we develop the minimal flavon-chromon preonic model where $\text{spin}\text{-}\text{1}\text{2}$ and spin-0 components of four preonic chiral multiplets correspond to flavons and chromons, from which quarks and leptons are made as composites. The emergence of the concepts of flavour and colour, in this minimal model, is synonymous with R and supersymmetry breaking. This breaking also gives a heavy mass to the gaugino, which is necessary for the implementation of the model.     

Semiclassical solutions ofOSp(N,4) supersymmetry 0

This work analyzes the connection between the so-called reflective boundary conditions and the spontaneous breaking of supersymmetry in anti-de Sitter background space. The one-loop effective potential of the Wess-Zumino model is computed using the supersymmetry invariant Pauli-Villars regularization procedure. The effect of the background geometry is determined exactly. It is shown that supersymmetry is preserved to the one-loop order at each classically supersymmetric extremum of the effective potential. Depending on the reflective boundary conditions chosen, quantum shifts in theA-field andB-field vacuum solutions are exhibited.     

Supersymmetry breaking for the observable sector in superstring models

We discuss the supersymmetry breaking in four-dimensional supergravity models from superstrings including perturbative or non-perturbative string σ-model corrections. It is found that various soft supersymmetry breaking terms can appear with values of the order ofm _3/2 even at the tree level of effective field theory and of string theory.     

Instanton effects in N = 2 supersymmetric quantum mechanics

Supersymmetric quantum mechanics with several bosonic and fermionic dynamic variables is considered. Two different N = 2 supersymmetric models involving instantons are discussed in detail. Instantons fail to break supersymmetry in one of the models considered. The vacuum state is degenerate in this model which generally results in spontaneous breaking of internal left-right symmetry. In another model supersymmetry is destroyed dynamically due to special complex instanton solutions. Possible implications for SUSY field theories are discussed.     

Dynamical breaking of supersymmetry and positivity of vacuum energy density

The possibility of dynamical breaking of supersymmetry is investigated with special emphasis on the role of the positivity of the vacuum energy density. We point out that (i) the vacuum energy density can become negative after appropriate renormalization of the fields (thereby being energetically favorable over the supersymmetric case), yet (ii) in such a situation the Nambu-Goldstone fermion state must necessarily possess negative norm, the theory becoming physically unacceptable. This phenomenon is explicitly demonstrated using an O(N) symmetric Wess-Zumino type model in the large-N limit. We conclude that for dynamical breaking of supersymmetry to occur in a physically acceptable manner, it is necessary that supersymmetric solution(s) be completely destroyed. Our study suggests that a strong power-type infrared singularity might achieve such a situation.     

Dynamical Breaking of Supersymmetry and Its Restoration at High Temperatures

The dynamical breaking of the supersymmetric Higgs model is discussed without adding the Fayet—Iliopoulos term to the Lagrangian. It is shown, in terms of the Nambu—Jona-Lasinio mechanism, that the supersymmetry breaking can be realized dynamically in the supersymmetric Higgs model. The supersymmetry behavior at finite temperatures is also investigated and it is shown that the supersymmetry broken dynamically at zero temperature can be restored at finite temperatures.     

Investigation of some supersymmetric decay channels of theZ

We consider the decay of the intermediate vector bosonZ into two fermions and two Goldstone fermions in a model realizing supersymmetry in a nonlinear way. Since the Goldstone fermions are neutrino-like particles, the experimental signature would be two leptons or two jets together with missing energy. We show that for a scale of spontaneous supersymmetry breaking of the order 70 GeV the rate for this process should be detectable in LEP-experiments.     

Radiative decays of quarkonia into Goldstone fermions

We consider the decay of³ S ₁ quarkonia into a photon and two Goldstone fermions in a model realizing supersymmetry in a nonlinear way. We derive a lower bound of 3.5 GeV for the scale of spontaneous supersymmetry breaking from Υ-decays. We show that the decay of a³ S ₁ quarkonium into two Goldstone fermions is forbidden in the order we consider.     

SUSY CP problem in gauge mediation model

SUSY CP problem in the gauge mediation supersymmetry breaking model is reconsidered. We pay particular attention to two sources of CP violating phases whose effects were not seriously studied before; one is the effect of the breaking of the GUT relation among the gaugino masses due to the field responsible for the GUT symmetry breaking, and the other is the supergravity effect on the supersymmetry breaking parameters, in particular, on the bi-linear supersymmetry breaking Higgs mass term. We show that both of them can induce too large electric dipole moments of electron, neutron, and so on, to be consistent with the experimental bounds.     

Decoupling in supersymmetric theories

We examine the decoupling of massive states in supergravity theories. Using superspace functional techniques to “integrate out” the massive modes we derive the effective low-energy lagrangian. The technique is extended to the case of large supersymmetry breaking and we show how the effective lagrangian correctly accounts for vacuum expectation values of massive fields. We discuss the structure of effective theories following from the superstring in which the effects of Kaluza-Klein modes and states massive after intermediate scale breaking are included. It is shown in the case of large intermediate scale breaking the theory should possess discrete symmetries to protect light states from large supersymmetry breaking and we list the conditions for viable models.     

Softly broken supersymmetry and the fine-tuning problem

The supersymmetry of the simple Wess-Zumino model is broken, in the tree-approximation, by adding all possible parity-even [mass]-dimension 2 and 3 terms. The model is then renormalized using BPHZ and the normal product algorithm, such that supersymmetry is only softly broken (in the original sense of Schroer and Symanzik).We show that, within the above renormalization scheme, none of the added breaking terms give rise to technical fine-tuning problems (defined in the sense of Gildener) in larger models, with scalar multiplets and hierarchy of mass scales, which is in contrast to what we obtain via analytic schemes such as dimensional renormalization, or supersymmetry extension of which.The discrepancy (which can be shown to persist in more general models) originates in the inherent local ambiguity in the finite parts of subtracted Feynman integrals. Emphasizing that the issue is purely technical (as opposed to physical) in origin, and that all physical properties are scheme-independent (as they should be!), we conclude that the technical fine-tuning problem, in the specific sense used in this paper, being scheme dependent, is not a well-defined issue within the context of renormalized perturbation theory.     

A custodial symmetry for the cosmological constant in the effective theories of four-dimensional superstrings

We discuss supersymmetry breaking in the effective supergravity theories of four-dimensional N = 1 superstrings. Improving a recent suggestion, we introduce a superpotential modification that describes spontaneous supersymmetry breaking with vanishing cosmological constant and Str M² = 0 at any minimum of the tree level potential. We prove that in a class of models there are classical minima at which also Str f(M² = 0 for any function f. In particular, the whole one-loop cosmological constant vanishes. We propose a new boson-fermion symmetry of the spectrum, relating the graviton and the “dilatino”, which explains these remarkable properties.