1,056 research outputs found
Discretization of the Superparticle Path Integral
Requiring that the path integral has the global symmetries of the classical
action and obeys the natural composition property of path integrals, and also
that the discretized action has the correct naive continuum limit, we find a
viable discretization of the (D=3,N=2) superparticle action.Comment: 10 page
How (Not) to Palatini
We revisit the problem of defining non-minimal gravity in the first order
formalism. Specializing to scalar-tensor theories, which may be disguised as
`higher-derivative' models with the gravitational Lagrangians that depend only
on the Ricci scalar, we show how to recast these theories as Palatini-like
gravities. The correct formulation utilizes the Lagrange multiplier method,
which preserves the canonical structure of the theory, and yields the
conventional metric scalar-tensor gravity. We explain the discrepancies between
the na\"ive Palatini and the Lagrange multiplier approach, showing that the
na\"ive Palatini approach really swaps the theory for another. The differences
disappear only in the limit of ordinary General Relativity, where an accidental
redundancy ensures that the na\"ive Palatini works there. We outline the
correct decoupling limits and the strong coupling regimes. As a corollary we
find that the so-called `Modified Source Gravity' models suffer from strong
coupling problems at very low scales, and hence cannot be a realistic
approximation of our universe. We also comment on a method to decouple the
extra scalar using the chameleon mechanism.Comment: 18 pages, LaTeX; added references and minor improvements in sec
Noncommutative Solitons: Moduli Spaces, Quantization, Finite Theta Effects and Stability
We find the N-soliton solution at infinite theta, as well as the metric on
the moduli space corresponding to spatial displacements of the solitons. We use
a perturbative expansion to incorporate the leading 1/theta corrections, and
find an effective short range attraction between solitons. We study the
stability of various solutions. We discuss the finite theta corrections to
scattering, and find metastable orbits. Upon quantization of the two-soliton
moduli space, for any finite theta, we find an s-wave bound state.Comment: Second revision: Discussions of translation zero-modes in section 4
and scales in section 5 improved; web addresses of movies changed. First
revision: Section 6 is rewritten (thanks to M. Headrick for pointing out a
mistake in the original version); some references and acknowledgements added.
21 pages, JHEP style, Hypertex, 1 figure, 3 MPEG's at:
http://www.physto.se/~unge/traj1.mpg http://www.physto.se/~unge/traj2.mpg
http://www.physto.se/~unge/traj3.mp
The deformed M2-brane
The superembedding formalism is used to study correction terms to the
dynamics of the M2 brane in a flat background. This is done by deforming the
standard embedding constraint. It is shown rigorously that the first such
correction occurs at dimension four. Cohomological techniques are used to
determine this correction explicitly. The action is derived to quadratic order
in fermions, and the modified \k-symmetry transformations are given.Comment: 38 pages, 3 figure
Kappa-symmetric non-abelian Born-Infeld actions in three dimensions
A superembedding construction of general non-abelian Born-Infeld actions in
three dimensions is described. These actions have rigid target space and local
worldvolume supersymmetry(i.e. kappa symmetry). The standard abelian
Born-Infeld gauge multiplet is augmented with an additional worldvolume SU(N)
gauge supermultiplet. It is shown how to construct single-trace actions and in
particular a kappa-supersymmetric extension of the symmetrised trace action.Comment: 14 page
Topological twisted sigma model with H-flux revisited
In this paper we revisit the topological twisted sigma model with H-flux. We
explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian
geometry. we show that the resulting action consists of a BRST exact term and
pullback terms, which only depend on one of the two generalized complex
structures and the B-field. We then discuss the topological feature of the
model.Comment: 16 pages. Appendix adde
On Superspace Chern-Simons-like Terms
We search for superspace Chern-Simons-like higher-derivative terms in the low
energy effective actions of supersymmetric theories in four dimensions.
Superspace Chern-Simons-like terms are those gauge-invariant terms which cannot
be written solely in terms of field strength superfields and covariant
derivatives, but in which a gauge potential superfield appears explicitly. We
find one class of such four-derivative terms with N=2 supersymmetry which,
though locally on the Coulomb branch can be written solely in terms of field
strengths, globally cannot be. These terms are classified by certain Dolbeault
cohomology classes on the moduli space. We include a discussion of other
examples of terms in the effective action involving global obstructions on the
Coulomb branch.Comment: 23 pages; a reference and an author email correcte
4D N = 2 Supergravity and Projective Superspace
This paper presents a projective superspace formulation for 4D N = 2
matter-coupled supergravity. We first describe a variant superspace realization
for the N = 2 Weyl multiplet. It differs from that proposed by Howe in 1982 by
the choice of the structure group (SO(3,1) x SU(2) versus SO(3,1) x U(2)),
which implies that the super-Weyl transformations are generated by a
covariantly chiral parameter instead of a real unconstrained one. We introduce
various off-shell supermultiplets which are curved superspace analogues of the
superconformal projective multiplets in global supersymmetry and which describe
matter fields coupled to supergravity. A manifestly locally supersymmetric and
super-Weyl invariant action principle is given. Off-shell locally
supersymmetric nonlinear sigma models are presented in this new superspace.Comment: 26 pages, LaTeX, no figures; V2: comments and references added,
version published in JHEP; V3: typo in eq. (2.7e) correcte
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