196 research outputs found
Interactions of N Goldstini in Superspace
We study field theories with N extended non-linearly realized
supersymmetries, describing the couplings of models that contain N goldstini.
We review all the known formulations of the N=1 goldstino theories and we
generalize them to an arbitrary number N of non-linearly realized
supersymmetries. We explicitly prove the equivalence of all these extended
supersymmetry breaking models containing N goldstini and reformulate the theory
with N supersymmetries in terms of standard N=1 constrained superfields.Comment: 29 pages, 1 table. v2: published version. Title changed, a reference
and some comments adde
On the origin of constrained superfields
In this work we analyze constrained superfields in supersymmetry and
supergravity. We propose a constraint that, in combination with the constrained
goldstino multiplet, consistently removes any selected component from a generic
superfield. We also describe its origin, providing the operators whose
equations of motion lead to the decoupling of such components. We illustrate
our proposal by means of various examples and show how known constraints can be
reproduced by our method.Comment: 20 pages, to be published in JHE
On the Starobinsky Model of Inflation from Supergravity
We discuss how the higher-derivative Starobinsky model of inflation
originates from N=1 supergravity. It is known that, in the old-minimal
supergravity description written by employing a chiral compensator in the
superconformal framework, the Starobinsky model is equivalent to a no-scale
model with F-term potential. We show that the Starobinsky model can also be
originated within the so-called new-minimal supergravity, where a linear
compensator superfield is employed. In this formulation, the Starobinsky model
is equivalent to standard supergravity coupled to a massive vector multiplet
whose lowest scalar component plays the role of the inflaton and the vacuum
energy is provided by a D-term potential. We also point out that higher-order
corrections to the supergravity Lagrangian represent a threat to the
Starobinsky model as they can destroy the flatness of the inflaton potential in
its scalar field equivalent description.Comment: 17 pages, 2 figures, published versio
The SU(2)-Higgs model on asymmetric lattices
We calculate the corrections to the coupling
anisotropies of the SU(2)-Higgs model on lattices with asymmetric lattice
spacings. These corrections are obtained by a one-loop calculation requiring
the rotational invariance of the gauge- and Higgs-boson propagators in the
continuum limit.Comment: 8 pages, latex, uses epsfig.sty, 5 postscript figures include
Supersymmetry Breaking and Inflation from Higher Curvature Supergravity
The generic embedding of the higher curvature theory into old-minimal
supergravity leads to models with rich vacuum structure in addition to its
well-known inflationary properties. When the model enjoys an exact R-symmetry,
there is an inflationary phase with a single supersymmetric Minkowski vacuum.
This appears to be a special case of a more generic set-up, which in principle
may include R-symmetry violating terms which are still of pure supergravity
origin. By including the latter terms, we find new supersymmetry breaking vacua
compatible with single-field inflationary trajectories. We discuss explicitly
two such models and we illustrate how the inflaton is driven towards the
supersymmetry breaking vacuum after the inflationary phase. In these models the
gravitino mass is of the same order as the inflaton mass. Therefore, pure
higher curvature supergravity may not only accommodate the proper inflaton
field, but it may also provide the appropriate hidden sector for supersymmetry
breaking after inflation has ended.Comment: 41 pages, 21 figures, published versio
Weak gravity versus de Sitter
We show that one can uncover a Dine-Seiberg problem for de Sitter critical
points in supergravity theories by utilizing the magnetic weak gravity
conjecture. We present a large variety of N=2 gauged supergravity models that
include vector multiplets and in all cases we find that the weak gravity
conjecture threatens de Sitter. A common feature in all such examples is a
degenerate mass matrix for the gravitini, which we therefore deem a swampland
criterion for de Sitter critical points.Comment: 29 pages. v2: minor corrections and references added. Published on
JHE
Numerical tests of the electroweak phase transition and thermodynamics of the electroweak plasma
The finite temperature phase transition in the SU(2) Higgs model at a Higgs
boson mass GeV is studied in numerical simulations on
four-dimensional lattices with time-like extensions up to . The effects
of the finite volume and finite lattice spacing on masses and couplings are
studied in detail. The errors due to uncertainties in the critical hopping
parameter are estimated. The thermodynamics of the electroweak plasma near the
phase transition is investigated by determining the relation between energy
density and pressure.Comment: latex2e, 32 pages, 11 figures with epsfig; A few comments and a new
table are adde
Decoupling of Layers in the Three-dimensional Abelian Higgs Model
The Abelian Higgs model with anisotropic couplings in 2+1 dimensions is
studied in both the compact and non-compact formulations. Decoupling of the
space-like planes takes place in the extreme anisotropic limit, so charged
particles and gauge fields are presumably localized within these planes. The
behaviour of the model under the influence of an external magnetic field is
examined in the compact case and yields further characterization of the phases.Comment: 23 pages, 12 figures, plain late
Three-Dimensional SU(3) gauge theory and the Spatial String Tension of the (3+1)-Dimensional Finite Temperature SU(3) Gauge Theory
We establish a close relation between the spatial string tension of the
(3+1)-dimensional gauge theory at finite temperature () and
the string tension of the 3-dimensional gauge theory () which
is similar to what has been found previously for . We obtain
and , respectively. For temperatures larger than twice the critical
temperature results are consistent with a temperature dependent coupling
running according to the two-loop -function with .Comment: 11 pages (4 figures
Dimensional Reduction, Hard Thermal Loops and the Renormalization Group
We study the realization of dimensional reduction and the validity of the
hard thermal loop expansion for lambda phi^4 theory at finite temperature,
using an environmentally friendly finite-temperature renormalization group with
a fiducial temperature as flow parameter. The one-loop renormalization group
allows for a consistent description of the system at low and high temperatures,
and in particular of the phase transition. The main results are that
dimensional reduction applies, apart from a range of temperatures around the
phase transition, at high temperatures (compared to the zero temperature mass)
only for sufficiently small coupling constants, while the HTL expansion is
valid below (and rather far from) the phase transition, and, again, at high
temperatures only in the case of sufficiently small coupling constants. We
emphasize that close to the critical temperature, physics is completely
dominated by thermal fluctuations that are not resummed in the hard thermal
loop approach and where universal quantities are independent of the parameters
of the fundamental four-dimensional theory.Comment: 20 pages, 13 eps figures, uses epsfig and pstrick
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