arXiv subjects

L. Bergamin

Publications and source records attributed to L. Bergamin.

26 records · Page 2Linked to original sources

arXiv2004

The Complete Solution of 2D Superfield Supergravity from graded Poisson-Sigma Models and the Super Pointparticle

Recently an alternative description of 2d supergravities in terms of graded Poisson-Sigma models (gPSM) has been given. As pointed out previously by the present authors a certain subset of gPSMs can be interpreted as "genuine" supergravity, fulfilling the well-known limits of supergravity, albeit deformed by the dilaton field. In our present paper we show that precisely that class of gPSMs corresponds one-to-one to the known dilaton supergravity superfield theories presented a long time ago by Park and Strominger. Therefore, the unique advantages of the gPSM approach can be exploited for the latter: We are able to provide the first complete classical solution for any such theory. On the other hand, the straightforward superfield formulation of the point particle in a supergravity background can be translated back into the gPSM frame, where "supergeodesics" can be discussed in terms of a minimal set of supergravity field degrees of freedom. Further possible applications like the (almost) trivial quantization are mentioned.

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arXiv2003

No Supersymmetry without Supergravity: Induced Supersymmetry Representations on Composite Effective Fields

Induced supersymmetry representations on composite operators are studied. In superspace the ensuing transformation rules (trivially) lead to an effective superfield. On the other hand, an induced representation must exist for non-linear (``on-shell'') supersymmetry as well. As this choice of the representation is physically irrelevant, any formulation of an effective action starting from the superspace representation must equally well be possible in a non-linear representation. We show that this leads to very relevant constraints on the formulation of effective actions in terms of composite operators. These ideas are applied to the simplest case of such a theory, N=1 SYM. It is shown that soft supersymmetry breaking within that theory forces one to include besides the Lagrangian multiplet S all currents of the super-conformal structure, embedded in a supergravity background, as relevant fields.

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arXiv2003

Dynamics of Glue-Balls in N=1 SYM Theory

The extension of the Veneziano-Yankielowicz effective Lagrangian with terms including covariant derivatives is discussed. This extension is important to understand glue-ball dynamics of the theory. Though the superpotential remains unchanged, the physical spectrum exhibits completely new properties.

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arXiv2003

Graded Poisson-Sigma Models and Dilaton-Deformed 2D Supergravity Algebra

Fermionic extensions of generic 2d gravity theories obtained from the graded Poisson-Sigma model (gPSM) approach show a large degree of ambiguity. In addition, obstructions may reduce the allowed range of fields as given by the bosonic theory, or even prohibit any extension in certain cases. In our present work we relate the finite W-algebras inherent in the gPSM algebra of constraints to algebras which can be interpreted as supergravities in the usual sense (Neuveu-Schwarz or Ramond algebras resp.), deformed by the presence of the dilaton field. With very straightforward and natural assumptions on them --like demanding rigid supersymmetry in a certain flat limit, or linking the anti-commutator of certain fermionic charges to the Hamiltonian constraint-- in the ``genuine'' supergravity obtained in this way the ambiguities disappear, as well as the obstructions referred to above. Thus all especially interesting bosonic models (spherically reduced gravity, the Jackiw-Teitelboim model etc.)\ under these conditions possess a unique fermionic extension and are free from new singularities. The superspace supergravity model of Howe is found as a special case of this supergravity action. For this class of models the relation between bosonic potential and prepotential does not introduce obstructions as well.

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arXiv2003

On the Effective Description of Dynamically Broken SUSY-Theories

We introduce a new class of effective actions describing dynamically broken supersymmetric theories in an essentially non-perturbative region. Our approach is a generalization of the known supersymmetric non-linear sigma models, but allows in contrast to the latter the description of dynamical supersymmetry breaking by non-perturbative non-semiclassical effects. This non-perturbative breaking mechanism takes place in confined theories, where the effective fields are composite operators. It is necessary within the context of quantum effective actions and the associated concept of symmetry breaking as a hysteresis effect. In this paper we provide a mathematical definition and description of the actions, its application to specific supersymmetic gauge theories is presented elsewhere.

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arXiv2003

SUSY Glue-Balls, Dynamical Symmetry Breaking and Non-Holomorphic Potentials

We discuss the instability of the Veneziano-Yankielowicz effective action (or its supersymmetric ground-state) with respect to higher order derivative terms. As such terms must be present in an effective action, the V-Y action alone cannot describe the dynamics of SYM consistently. We introduce an extension of this action, where all instabilities are removed by means of a much richer structure of the Kaehler potential. We demonstrate that the dominant contributions to the effective potential are determined by the non-holomorphic part of the action and we prove that the non-perturbative ground-state can be equipped with stable dynamics. Making an expansion near the resulting ground-state to second order in the derivatives never leads back to the result by Veneziano and Yankielowicz. As a consequence new dynamical effects arise, which are interpreted as the formation of massive states in the boson sector (glueballs) and are accompanied by dynamical supersymmetry breaking. As this regime of the dynamics is not captured by standard semi-classical analysis (instantons etc.), our results do not contradict these calculations but investigate the physics of the system beyond these approximations.

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arXiv2002

Dynamical Symmetry Breaking in SYM Theories as a Non-Semiclassical Effect

We study supersymmetry breaking effects in N=1 SYM from the point of view of quantum effective actions. Restrictions on the geometry of the effective potential from superspace are known to be problematic in quantum effective actions, where explicit supersymmetry breaking can and must be studied. On the other hand the true ground state can be determined from this effective action, only. We study whether some parts of superspace geometry are still relevant for the effective potential and discuss whether the ground states found this way justify a low energy approximation based on this geometry. The answer to both questions is negative: Essentially non-semiclassical effects change the behavior of the auxiliary fields completely and demand for a new interpretation of superspace geometry. These non-semiclassical effects can break supersymmetry.

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arXiv2000

Dynamical Symmetry Breaking and Static Limits of Extended Super-Yang-Mills Theories: A non-Seiberg-Wittian Approach

From a supersymmetry covariant source extension of N=2 SYM we study non-trivial thermodynamical limits thereof. Using an argument by one of us about the solution of the strong CP problem and the uniqueness of the QCD ground state we find that the dependence of the effective potential on the defining field operators is severely restricted. In contrast to the solution by Seiberg and Witten an acceptable infrared behavior only exists for broken supersymmetry while the gauge symmetry remains unbroken.

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