Scale Of Gaugino Condensation Research Articles

Anomaly mediation in local effective theories

The phenomenon known as ``anomaly mediation" can be understood in a variety of ways. Rather than an anomaly, certain gaugino bilinear terms are required by local supersymmetry and gauge invariance (the derivation of these terms is in some cases related to anomalies in scale invariance or $R$ symmetries). We explain why the gaugino bilinear is required in supersymmetric gauge theories with varying number of colors and flavors. By working in the Higgs phase, gauging a flavor group, or working below the scale of gaugino condensation, each of these theories has a local effective description in which we can identify the bilinear term, establishing its necessity in the microscopic theory. For example, in theories that exhibit gaugino condensation, the potential in the very low energy theory is supersymmetric precisely due to the relation between the nonperturbative superpotential and the gaugino bilinear terms. Similarly, the gravitino mass appears from its coupling to the gaugino bilinear.

On inflation in the presence of a gaugino condensate

We study the effect of inflation on gaugino condensation in supergravity. Unless the Hubble scale H is significantly below the gaugino condensation scale, the gaugino condensate is a dynamical variable which cannot be integrated out. For a sufficiently high H, the gaugino condensate evolves to zero which in turn leads to dilaton/moduli destabilization. In practice, this often occurs at the Hubble rate about an order of magnitude below the gaugino condensation scale. This effect is independent of the specifics of moduli stabilization and thus places model-independent constraints on inflationary scenarios. It also applies more generally to any periods of fast expansion in the early Universe.

Gaugino condensation scale of one family hidden [formula omitted], dilaton stabilization and gravitino mass

The hidden SU(5)′ with one family, 10′ and 5¯′, breaks supersymmetry dynamically. From the effective Lagrangian approach, we estimate the hidden sector gaugino condensation scale, the dilaton stabilization and the resulting gravitino mass. In some models, this gravitino mass can be smaller than the previous naive estimate. Then, it is possible to raise the SU(5)′ confining scale above 1013 GeV.

Heterotic mini-landscape (II): Completing the search for MSSM vacua in a [formula omitted] orbifold

We complete our search for MSSM vacua in the Z6-II heterotic orbifold by including models with 3 Wilson lines. We estimate the total number of inequivalent models in this orbifold to be 107. Out of these, we find almost 300 models with the exact MSSM spectrum, gauge coupling unification and a heavy top quark. Models with these features originate predominantly from local GUTs. The scale of gaugino condensation in the hidden sector is correlated with properties of the observable sector such that soft masses in the TeV range are preferred.

De Sitter vacua from matter superpotentials

Consistent uplifting of AdS vacua in string theory often requires extra light degrees of freedom in addition to those of a (Kähler) modulus. Here we consider the possibility that de Sitter and Minkowski vacua arise due to hidden sector matter interactions. We find that, in this scheme, the hierarchically small supersymmetry breaking scale can be explained by the scale of gaugino condensation and that interesting patterns of the soft terms arise. In particular, a matter-dominated supersymmetry breaking scenario and a version of the mirage mediation scheme appear in the framework of spontaneously broken supergravity.

Inflation and Kähler stabilization of the dilaton

The problems of attempting inflationary model-building in a theory containing a dilaton are explained. In particular, I study the shape of the dilaton potential today and during inflation, based on a weakly-coupled heterotic string model where corrections to the Kahler potential are assumed to be responsible for dilaton stabilization. Although no specific model-building is attempted, if the inflationary energy density is related to the scale of gaugino condensation, then the dilaton may be stabilized close enough to today's value that there is no significant change in the GUT scale coupling. This can occur in a very wide range of models, and helps to provide some justification for the standard predictions of the spectral index. I explain how this result can ultimately be traced to the supersymmetry structure of the theory.

Supersymmetric model of neutrino mass and leptogenesis with string-scale unification

Adjoint supermultiplets (1,3,0) and (8,1,0) modify the evolution of gauge couplings. If the unification of gauge couplings occurs at the string scale, their masses are fixed at around $10^{13}$ GeV. This scale coincides with expected gaugino condensation scale in the hidden sector $M_{string}^{2/3} m^{1/3}_{3/2} \sim 10^{13}$ GeV. We show how neutrino masses arise in this unified model which naturally explain the present atmospheric and solar neutrino data. The out-of-equilibrium decay of the superfield (1,3,0) at $10^{13}$ GeV may also lead to a lepton asymmetry which then gets converted into the present observed baryon asymmetry of the Universe.

Dilaton stabilisation in D-term inflation

Dilaton stabilisation is usually considered to pose a serious obstacle to successful D-term inflation in superstring theories. We argue that the physics of gaugino condensation is likely to be modified during the inflationary phase in such a way as to enhance the gaugino condensation scale. This enables the dilaton stabilisation during inflation with the D-term still dominating the vacuum energy at the stable minimum.

One-loop correction and the dilaton runaway problem

We examine the one-loop vacuum structure of an effective theory of gaugino condensation coupled to the dilaton for string models in which the gauge coupling constant does not receive string threshold corrections. The new ingredients in our treatment are that we take into account the one-loop correction to the dilaton K\"ahler potential and we use a formulation which includes a chiral field $H$ corresponding to the gaugino bilinear. We find through explicit calculation that supersymmetry in the Yang-Mills sector is broken by gaugino condensation. The dilaton and $H$ field have masses on the order of the gaugino condensation scale independently of the dilaton VEV. Although the calculation performed here is at best a model of the full gaugino condensation dynamics, the result shows that the one-loop correction to the dilaton K\"ahler potential as well as the detailed dynamics at the gaugino condensation scale may play an important role in solving the dilaton runaway problem.

Gaugino condensation and the anomalous U(1)

We study gaugino condensation in presence of an anomalous U(1) gauge group and find that global supersymmetry is dynamically broken. An example of particular interest is provided by effective string models with 4-dimensional Green-Schwarz anomaly cancellation mechanism. The structure of the hidden sector is constrained by the anomaly cancellation conditions and the scale of gaugino condensation is shifted compared with the usual case. We explicitly compute the resulting soft supersymmetry breaking terms.

Cosmological constraints on the scale of supersymmetry breaking

We consider the cosmological and astrophysical constraints on the decay of massive E 8 × E 8′ superstring axions associated with the hidden sector. We find that decay lifetimes greater than 1 s are ruled out by limits from nucleosynthesis, by limits on the distortion of the cosmic microwave and gamma ray backgrounds and by closure arguments. We conclude that Λ > 1.2 × 10 13 GeV, where Λ is the scale of gaugino condensation in the hidden sector. This implies that the scale of supersymmetry breaking is greater than 10 10 GeV. Significantly, our result agrees with the value of 5 x 10 13 GeV for Λ obtained independently by setting supersymmetric scalar masses equal to m w .

A Variant Approach in Superstring Phenomenology

A new phenomenological assumption is proposed to construct a unified model based on 4-dimensional string theories, and it is applied to a Z 7 orbifold model. We show that a gaugino condensation scale in a bidden sector is around 10 13 GeV which induces naturally soft supersymmetry breaking masses ∼ O(1) TeV in the observed sector

THE SCALE WHERE SUPERSYMMETRY BREAKS: A NEW PARAMETER IN UNIFIED MODELS

We examine supersymmetry breaking in string-inspired models through gaugino condensation in the hidden sector. With the physically sensible assumption that observable supersymmetry breaking effects turn off above the gaugino condensation scale (Λh), we derive a realistic range for the scale where supersymmetry breaks (1012 GeV<ΛSUSY= Λh<1016 GeV) which should be contrasted with the usual identification of ΛSUSY with the gauge coupling unification scale. We also derive constraints on the hidden sector to be consistent with this ΛSUSY range and to allow supersymmetry breaking with a perturbative gauge coupling in two-gaugino-condensate models. We then establish ΛSUSY as a new parameter in two unified models, the supersymmetric standard model (SSM), and the string-inspired standard model (SISM). We briefly review the two models, examining radiative electroweak breaking and the resulting phenomenology to determine allowed regions in parameter space as a function of ΛSUSY for a few representative cases. We also propose an algebraic combination of sparticle masses, which only depends on ΛSUSY, as a means of experimentally determining the scale at which supersymmetry breaks.

Cosmological implications of domain walls due to duality invariant moduli sector of superstring vacua

We study cosmological implications of the duality (PSL(2, Z )) invariant potential for the compactification radius T, arising in a class of superstring vacua. We show that in spite of having only one minimum in the fundamental domain of the T field there are two types of non-supersymmetric domain walls: one is associated with the discrete Peccei-Quinn symmetry T→ T+i, analogous to the axionic domain wall, and another one associated with the noncompact symmetry T→ 1 T , analogous to the Z 2 domain walls. The first one is bound by stringy cosmic strings. The scale of such domain walls is governed by the scale of gaugino condensation (O(10 16 GeV) in the case of the hidden E 8 gauge group), while the separation between minima is of the order of M Pl. We discuss the formation of walls and their cosmological implications: the walls must be gotten rid of, either by chopping by stringy cosmic strings and/or inflation. Since there is no Kibble mechanism to create strings, either one must assume they exist ab initio, or one must conclude that string cosmologies require inflation. The non-perturbative potential dealt with here appears not to give the needed inflationary epoch.