2,303 research outputs found
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.Comment: 37 pages, LaTex. Version 3: many important changes, extended
discussion of the topi
Generalized complex geometry and the Poisson Sigma Model
The supersymmetric Poisson Sigma model is studied as a possible worldsheet
realization of generalized complex geometry. Generalized complex structures
alone do not guarantee non-manifest N=(2,1) or N=(2,2) supersymmetry, but a
certain relation among the different Poisson structures is needed. Moreover,
important relations of an additional almost complex structure are found, which
have no immediate interpretation in terms of generalized complex structures.Comment: 13 pages, LaTeX. v2: references added, typos, v3: more typos,
references updated, final versio
Transformation Acoustics in Generic Elastic Media
In this work a transformation acoustics scheme for generic elastic media is
developed. Our approach starts form the decomposition of the elasticity tensor
in terms of its eigentensors, an idea previously used by Norris. While Norris'
transformation acoustics is restricted to the special class of so-called
pentamode materials, we show that a similar scheme can be defined for the most
general elasticity tensor. As in case of Norris' model (and in sharp contrast
to transformation optics), the compatibility equations of the transformation
medium are not purely algebraic and it is not guaranteed that solutions to
these equations exist for any choice of material parameters and coordinate
transformation. Nonetheless, it is shown that our scheme yields new cloaking
solutions for certain classes of materials. In particular, we present the first
application of a transformation based device for a non-scalar wave equation
outside of the field of electromagnetics.Comment: 14 pages, LaTe
Two-Dimensional N=(2,2) Dilaton Supergravity from Graded Poisson-Sigma Models I: Complete Actions and Their Symmetries
The formalism of graded Poisson-sigma models allows the construction of
N=(2,2) dilaton supergravity in terms of a minimal number of fields. For the
gauged chiral U(1) symmetry the full action, involving all fermionic
contributions, is derived. The twisted chiral case follows by simple
redefinition of fields. The equivalence of our approach to the standard second
order one in terms of superfields is presented, although for the latter so far
only the bosonic part of the action seems to have been available in the
literature. It is shown how ungauged models can be obtained in a systematic way
and some relations to relevant literature in superstring theory are discussed.Comment: 26 p., LaTeX. v3: extended version, new title, new section on
ungauged model
Two-Dimensional N=(2,2) Dilaton Supergravity from Graded Poisson-Sigma Models II: Analytic Solution and BPS States
The integrability of N=(2,2) dilaton supergravity in two dimensions is
studied by the use of the graded Poisson Sigma model approach. Though important
differences compared to the purely bosonic models are found, the general
analytic solutions are obtained. The latter include minimally gauged models as
well as an ungauged version. BPS solutions are an especially interesting
subclass.Comment: 23 p LaTe
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