211 research outputs found
Pole inflation in Jordan frame supergravity
We investigate inflation models in Jordan frame supergravity, in which an
inflaton non-minimally couples to the scalar curvature. By imposing the
condition that an inflaton would have the canonical kinetic term in the Jordan
frame, we construct inflation models with asymptotically flat potential through
pole inflation technique and discuss their relation to the models based on
Einstein frame supergravity. We also show that the model proposed by Ferrara et
al. has special position and the relation between the K\"ahler potential and
the frame function is uniquely determined by requiring that scalars take the
canonical kinetic terms in the Jordan frame and that a frame function consists
only of a holomorphic term (and its anti-holomorphic counterpart) for symmetry
breaking terms. Our case corresponds to relaxing the latter condition.Comment: 27 pages, 1 figure; revised version of the manuscript, accepted for
publication in JCA
Higher derivative scalar-tensor theory through a non-dynamical scalar field
We propose a new class of higher derivative scalar-tensor theories without
the Ostrogradsky's ghost instabilities. The construction of our theory is
originally motivated by a scalar field with spacelike gradient, which enables
us to fix a gauge in which the scalar field appears to be non-dynamical. We dub
such a gauge as the spatial gauge. Though the scalar field loses its dynamics,
the spatial gauge fixing breaks the time diffeomorphism invariance and thus
excites a scalar mode in the gravity sector. We generalize this idea and
construct a general class of scalar-tensor theories through a non-dynamical
scalar field, which preserves only spatial covariance. We perform a Hamiltonian
analysis and confirm that there are at most three (two tensors and one scalar)
dynamical degrees of freedom, which ensures the absence of a degree of freedom
due to higher derivatives. Our construction opens a new branch of scalar-tensor
theories with higher derivatives.Comment: 19 pages, 1 figure; v2 matching the JCAP versio
New Cosmological Solutions in Massive Gravity
We find new, simple cosmological solutions with flat, open, and closed
spatial geometries, contrary to the previous wisdom that only the open model is
allowed. The metric and the St\"{u}ckelberg fields are given explicitly,
showing nontrivial configurations of the St\"{u}ckelberg in the usual
Friedmann-Lema\^{i}tre-Robertson-Walker coordinates. The solutions exhibit
self-acceleration, while being free from ghost instabilities. Our solutions can
accommodate inhomogeneous dust collapse represented by the
Lema\^{i}tre-Tolman-Bondi metric as well. Thus, our results can be used not
only to describe homogeneous and isotropic cosmology but also to study
gravitational collapse in massive gravity.Comment: 5 page
Up-Regulation of the Brain and Purkinje-Cell Forms of Dystrophin Transcripts, in Becker Muscular Dystrophy
Farrando Sicilia, Jordi; Llauradó Grau, Josep M. ; Fuente Fuente, Carlos; Montes, Antoni
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