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Jonathan Bagger

Publications and source records attributed to Jonathan Bagger.

At least 37 records · Page 2Linked to original sources
arXiv2002

Generalized symmetry breaking on orbifolds

We reconsider the phenomenon of mass generation via coordinate-dependent compatifications of higher-dimensional theories on orbifolds. For definiteness, we study a generic five-dimensional (5D) theory compactified on S^1/Z_2. We show that the presence of fixed points, where the fields or their derivatives may be discontinuous, permits new realizations of the Scherk-Schwarz mechanism where, for example, the mass terms are localized at the orbifold fixed points. Our technique can be used to describe the explicit breaking of global flavor symmetries and supersymmetries by brane-localized mass terms. It can also be applied to the spontaneous breaking of local symmetries, such as gauge symmetries or supergravities.

hep-th↗
arXiv2001

Spacetime Supersymmetry in a nontrivial NS-NS Superstring Background

In this paper we consider superstring propagation in a nontrivial NS-NS background. We deform the world sheet stress tensor and supercurrent with an infinitesimal B_{μν} field. We construct the gauge-covariant super-Poincare generators in this background and show that the B_{μν} field spontaneously breaks spacetime supersymmetry. We find that the gauge-covariant spacetime momenta cease to commute with each other and with the spacetime supercharges. We construct a set of "magnetic" super-Poincare generators that are conserved for constant field strength H_{μνλ}, and show that these generators obey a "magnetic" extension of the ordinary supersymmetry algebra.

hep-th↗
arXiv2000

Quantum Inconsistency of Einstein Supergravity

We show that N=1, D=4 Einstein-frame supergravity is inconsistent at one loop because of an anomaly in local supersymmetry transformations. A Jacobian must be added to the Einstein-frame Lagrangian to cancel this anomaly. We show how the Jacobian arises from the super-Weyl field redefinition that takes the superspace Lagrangian to the Einstein frame. We present an explicit example which demonstrates that the Jacobian is necessary for one-loop scattering amplitudes to be frame independent.

hep-th↗
arXiv2000

Anomaly mediation in supergravity theories

We consider the effects of anomalies on the supersymmetry-breaking parameters in supergravity theories. We construct a supersymmetric expression for the anomaly-induced terms in the 1PI effective action; we use this result to compute the complete one-loop formula for the anomaly-induced gaugino mass. The mass receives contributions from the super-Weyl, Kahler, and sigma-model anomalies of the supergravity theory. We point out that the anomaly-mediated gaugino mass can be affected by local counterterms that cancel the super-Weyl-Kahler anomaly. This implies that the gaugino mass cannot be predicted unless the full high-energy theory is known.

hep-th↗
arXiv1999

Dual Anti-de Sitter Superalgebras from Partial Supersymmetry Breaking

The partial breaking of supersymmetry in anti-de Sitter (AdS) space can be accomplished using two of four dual representations for the massive OSp(1,4) spin-3/2 multiplet. The representations can be ``unHiggsed,'' which gives rise to a set of dual N=2 supergravities and supersymmetry algebras.

hep-th↗
arXiv1999

Gaugino Condensation in N=1 Supergravity Models with Multiple Dilaton-Like Fields

We study supersymmetry breaking by hidden-sector gaugino condensation in N=1 D=4 supergravity models with multiple dilaton-like moduli fields. Our work is motivated by Type I string theory, in which the low-energy effective Lagrangian can have different dilaton-like fields coupling to different sectors of the theory. We construct the effective Lagrangian for gaugino condensation and use it to compute the visible-sector gaugino masses. We find that the gaugino masses can be of order the gravitino mass, in stark contrast to heterotic string models with a single dilaton field.

hep-th↗
arXiv1999

Naturally Heavy Scalars in Supersymmetric Grand Unified Theories

The supersymmetric flavor, CP and Polonyi problems are hints that the fundamental scale of the soft supersymmetry breaking parameters may be above a TeV, in apparent conflict with naturalness. We consider the possibility that multi-TeV scalar masses are generated by Planck- or unification-scale physics, and find the conditions under which the masses of scalars with large Yukawa couplings are driven, radiatively and asymptotically, to the weak scale through renormalization group evolution. Light third generation scalars then satisfy naturalness, while first and second generation scalars remain heavy to satisfy experimental constraints. We find that this mechanism is beautifully realized in the context of grand unified theories. In particular, the existence of right-handed neutrinos plays an important role in allowing remarkably simple scenarios. For example, for SO(10) boundary conditions with the squared masses of Higgs scalars double those of sleptons and squarks, we find that the entire scalar mass scale may be increased to 4 TeV at the unification scale without sacrificing naturalness.

hep-ph↗
arXiv1997

The tensor Goldstone multiplet for partially broken supersymmetry

We show that the tensor gauge multiplet of N=1 supersymmetry can serve as the Goldstone multiplet for partially broken rigid N=2 supersymmetry. We exploit a remarkable analogy with the Goldstone-Maxwell multiplet of hep-th/9608177 to find its nonlinear transformation law and its invariant Goldstone action. We demonstrate that the tensor multiplet has two dualities. The first transforms it into the chiral Goldstone multiplet; the other leaves it invariant.

hep-th↗
arXiv1997

Higgs Mechanism in String Theory

In first-quantized string theory, spacetime symmetries are described by inner automorphisms of the underlying conformal field theory. In this paper we use this approach to illustrate the Higgs effect in string theory. We consider string propagation on M^{24,1} \times S^1, where the circle has radius R, and study SU(2) symmetry breaking as R moves away from its critical value. We find a gauge-covariant equation of motion for the broken-symmetry gauge bosons and the would-be Goldstone bosons. We show that the Goldstone bosons can be eliminated by an appropriate gauge transformation. In this unitary gauge, the Goldstone bosons become the longitudinal components of massive gauge bosons.

hep-th↗
arXiv1996

New Goldstone multiplet for partially broken supersymmetry

The partial spontaneous breaking of rigid N=2 supersymmetry implies the existence of a massless N=1 Goldstone multiplet. In this paper we show that the spin-(1/2,1) Maxwell multiplet can play this role. We construct its full nonlinear transformation law and find the invariant Goldstone action. The spin-1 piece of the action turns out to be of Born-Infeld type, and the full superfield action is duality invariant. This leads us to conclude that the Goldstone multiplet can be associated with a D-brane solution of superstring theory for p=3. In addition, we find that N=1 chirality is preserved in the presence of the Goldstone-Maxwell multiplet. This allows us to couple it to N=1 chiral and gauge field multiplets. We find that arbitrary Kahler and superpotentials are consistent with partially broken N=2 supersymmetry.

hep-th↗
arXiv1995

Destabilizing Divergences in Supergravity Theories at Two Loops

We examine the stability of the mass hierarchy in hidden-sector supergravity theories. We show that a quadratically divergent tadpole can appear at two loops, even in minimal supergravity theories, provided the theory has a gauge- and global-symmetry singlet with renormalizable couplings to the visible fields. This tadpole can destabilize the hierarchy. We also find a quadratically divergent two-loop contribution to the field-dependent vacuum energy. This result casts doubt on the efficacy of the "LHC mechanism" for controlling quadratic divergences. We carry out the two-loop calculation in a manifestly supersymmetric formalism, and explain how to apply the formalism in the presence of supersymmetry breaking to derive radiative corrections to the supersymmetric and soft supersymmetry-breaking operators. Our approach greatly simplifies the calculation and guarantees consistency of our results with the underlying supergravity framework.

hep-ph↗
arXiv1995

Precise Predictions for the Masses and Couplings in the Minimal Supersymmetric Standard Model

We present selected results of our program to determine the masses, gauge couplings, and Yukawa couplings of the minimal supersymmetric model in a full one-loop calculation. We focus on the precise prediction of the strong coupling alpha_s(M_Z) in the context of supersymmetric unification. We discuss the importance of including the finite corrections and demonstrate that the leading-logarithmic approximation can significantly underestimate alpha_s(M_Z) when some superpartner masses are light. We show that if GUT thresholds are ignored, and the superpartner masses are less than about 500 GeV, the prediction for alpha_s(M_Z) is quite large. We impose constraints from nucleon decay experiments and find that minimal SU(5) GUT threshold corrections increase alpha_s(M_Z) over most of the parameter space. We also consider the missing-doublet SU(5) model and find that it predicts preferred values for the strong coupling, even for a very light superpartner spectrum. We briefly discuss predictions for the bottom-quark mass in the small tan beta region.

hep-ph↗
arXiv1995

Dynamical Supersymmetry Breaking in Supergravity Theories

In rigid supersymmetry, generic models of dynamical supersymmetry breaking contain a light Goldstone boson, called the R axion. We show that supergravity effects explicitly break the R symmetry and give mass to the R axion. For visible and renormalizable hidden sector models, the massive R axion is free from astrophysical and cosmological problems. For nonrenormalizable hidden sector models, the R axion suffers from cosmological difficulties similar to those of the moduli fields in string theory.

hep-ph↗
arXiv1995

Precision Corrections to Supersymmetric Unification

We compute the full set of weak-scale gauge and Yukawa threshold corrections in the minimal supersymmetric standard model, including all finite (non-logarithmic) corrections, which we show to be important. We use our results to examine the effects of unification-scale threshold corrections in the minimal and missing-doublet SU(5) models. We work in the context of a unified mass spectrum, with scalar mass M_0 and gaugino mass M_1/2, and find that in minimal SU(5) with squark masses less than one TeV, successful gauge and Yukawa coupling unification requires M_1/2 << M_0 and M_0 \simeq 1 TeV. In contrast, we find that the missing-doublet model permits gauge and Yukawa unification for a wide range of supersymmetric masses.

hep-ph↗