30,385 research outputs found
IEAD: A Novel One-Line Interface to Query Astronomical Science Archives
In this article I present IEAD, a new interface for astronomical science
databases. It is based on a powerful, yet simple, syntax designed to completely
abstract the user from the structure of the underlying database. The
programming language chosen for its implementation, JavaScript, makes it
possible to interact directly with the user and to provide real-time
information on the parsing process, error messages, and the name resolution of
targets; additionally, the same parsing engine is used for context-sensitive
autocompletion. Ultimately, this product should significantly simplify the use
of astronomical archives, inspire more advanced uses of them, and allow the
user to focus on what scientific research to perform, instead of on how to
instruct the computer to do it.Comment: 13 pages, PASP in pres
On the stability of field-theoretical regularizations of negative tension branes
Any attempt to regularize a negative tension brane through a bulk scalar
requires that this field is a ghost. One can try to improve in this aspect in a
number of ways. For instance, it has been suggested to employ a field whose
kinetic term is not sign definite, in the hope that the background may be
overall stable. We show that this is not the case; the physical perturbations
(gravity included) of the system do not extend across the zeros of the kinetic
term; hence, all the modes are entirely localized either where the kinetic term
is positive, or where it is negative; this second type of modes are ghosts. We
show that this conclusion does not depend on the specific choice for the
kinetic and potential functions for the bulk scalar.Comment: 7 pages, 3 figure
Polaron Crossover in Molecular Solids
An analytical variational method is applied to the molecular Holstein
Hamiltonian in which the dispersive features of the dimension dependent phonon
spectrum are taken into account by a force constant approach. The crossover
between a large and a small size polaron is monitored, in one, two and three
dimensions and for different values of the adiabatic parameter, through the
behavior of the effective mass as a function of the electron-phonon coupling.
By increasing the strength of the inter-molecular forces the crossover becomes
smoother and occurs at higher {\it e-ph} couplings. These effects are more
evident in three dimensions. We show that our Modified Lang-Firsov method
starts to capture the occurence of a polaron self-trapping transition when the
electron energies become of order of the phonon energies. The self-trapping
event persists in the fully adiabatic regime. At the crossover we estimate
polaron effective masses of order times the bare band mass
according to dimensionality and value of the adiabatic parameter. Modified
Lang-Firsov polaron masses are substantially reduced in two and three
dimensions. There is no self-trapping in the antiadiabatic regime.Comment: To be published in J.Phys.:Condensed Matte
Deterministic Controlled-NOT gate for single-photon two-qubit quantum logic
We demonstrate a robust implementation of a deterministic linear-optical
Controlled-NOT (CNOT) gate for single-photon two-qubit quantum logic. A
polarization Sagnac interferometer with an embedded 45-oriented dove
prism is used to enable the polarization control qubit to act on the momentum
(spatial) target qubit of the same photon. The CNOT gate requires no active
stabilization because the two spatial modes share a common path, and it is used
to entangle the polarization and momentum qubits.Comment: 10 pages, 4 figures. Typos corrected, referee comments and
correction
Constraining auto-interaction terms in α-attractor supergravity models of inflation
The inflationary mechanism has become the paradigm of modern cosmology over the last thirty years. However, there are several aspects of inflationary physics that are still to be addressed, like the shape of the inflationary potential. Regarding this, the so-called α-attractor models show interesting properties. In this work, the reconstruction of the effective potential around the global minimum of these particular potentials is provided, assuming a detection of permille-order for the tensor-to-scalar-ratio by forthcoming cosmic microwave background or gravitational waves experiments
Reconstruction of -attractor supergravity models of inflation
In this paper, we apply reconstruction techniques to recover the potential
parameters for a particular class of single-field models, the
-attractor (supergravity) models of inflation. This also allows to
derive the inflaton vacuum expectation value at horizon crossing. We show how
to use this value as one of the input variables to constrain the
postaccelerated inflationary phase. We assume that the tensor-to-scalar ratio
is of the order of , a level reachable by the expected
sensitivity of the next-generation CMB experiments.Comment: 10 pages, LaTeX, some typos correcte
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