1,169 research outputs found
General Relativity as an Attractor in Scalar-Tensor Stochastic Inflation
Quantum fluctuations of scalar fields during inflation could determine the
very large-scale structure of the universe. In the case of general
scalar-tensor gravity theories these fluctuations lead to the diffusion of
fundamental constants like the Planck mass and the effective Brans--Dicke
parameter, . In the particular case of Brans--Dicke gravity, where
is constant, this leads to runaway solutions with infinitely large
values of the Planck mass. However, in a theory with variable we find
stationary probability distributions with a finite value of the Planck mass
peaked at exponentially large values of after inflation. We conclude
that general relativity is an attractor during the quantum diffusion of the
fields.Comment: LaTeX (with RevTex) 11 pages, 2 uuencoded figures appended, also
available on WWW via http://star.maps.susx.ac.uk/index.htm
Southern Hemisphere Observations of a eV Cosmic Ray Source Near the Direction of the Galactic Centre
We report on an analysis of data from the southern hemisphere SUGAR cosmic
ray detector. We confirm the existence of an excess of eV cosmic rays
from a direction close to the Galactic Centre, first reported by the AGASA
group. We find that the signal is consistent with that from a point source, and
we find no evidence for an excess of cosmic rays coming from the direction of
the Galactic Centre itself.Comment: 14 pages including 5 postscript figures, corrected the title
(replaced "Cosmic Ray Source" instead of "Cosmic Ray"
STATIONARY SOLUTIONS IN BRANS-DICKE STOCHASTIC INFLATIONARY COSMOLOGY
In Brans-Dicke theory the Universe becomes divided after inflation into many
exponentially large domains with different values of the effective
gravitational constant. Such a process can be described by diffusion equations
for the probability of finding a certain value of the inflaton and dilaton
fields in a physical volume of the Universe. For a typical chaotic inflation
potential, the solutions for the probability distribution never become
stationary but grow forever towards larger values of the fields. We show here
that a non-minimal conformal coupling of the inflaton to the curvature scalar,
as well as radiative corrections to the effective potential, may provide a
dynamical cutoff and generate stationary solutions. We also analyze the
possibility of large nonperturbative jumps of the fluctuating inflaton scalar
field, which was recently revealed in the context of the Einstein theory. We
find that in the Brans--Dicke theory the amplitude of such jumps is strongly
suppressed.Comment: 19 pages, LaTe
Ahorro energético en riego por aspersión. Pruebas de nuevos aspersores en banco automático con viento
El consumo energético en regadío es directamente proporcional a los valores
objetivos de presión de una red colectiva de riego presurizada. El sistema de riego en
parcela que más condiciona esta presión objetivo es el riego por aspersión. En este trabajo
se ha analizado el comportamiento de los aspersores más utilizados en España en
condiciones normales de funcionamiento frente a condiciones de presiones más bajas. Para
ello se utilizó un banco de ensayo automático con viento y otro en condiciones confinadas
sin viento. Se analizaron los aspersores en múltiples condiciones de trabajo, priorizando en
el estudio la variable presión. Para ello se contempló un rango de presiones de 1,5 bar a 3.5
bar y con dos regímenes de viento: sin viento y con viento moderado. Como resultados del
estudio se ofrece un análisis global de los datos obtenidos, que justifican la posibilidad de
reducir la presión en riego por aspersión Además, se profundiza en resultados concretos
para la reducción de la presión en el marco de riego de doce por quince metros
DIFFERENTIAL TEMPORAL AND SPATIAL DISTRIBUTION OF ADULT LOGGERHEAD SEA TURTLES FROM GULF OF CÁDIZ TO WESTERN MEDITERRANEAN SEA
The aim of this paper was to search for and model spatial and seasonal trends in
occurrences (stranding or by-catches) of adult loggerhead turtles in the western Mediterranean
area and Gulf of Cádiz (Atlantic) independently of their origin. Adult turtles were only bycaught
on longlines from May to August. Adults were stranded in the eastern and western areas of the
Strait of Gibraltar threshold throughout the year. In the Gulf of Cádiz (Atlantic), strandings were
significantly concentrated in May and June, whereas in the Alboran Sea (Mediterranean), strandings
mainly occurred in June and July. The probability of catching a mature loggerhead increases
during June and July south of the Balearic Islands. The results suggest that adult loggerhead
turtles move (migrate) from the Atlantic area (Gulf of Cádiz) to the Mediterranean (Alboran
Sea) from May to June, and subsequently move to the Balearic Sea from June to July. These
results are in line with those obtained by previous studies.Postprin
Constraints from Inflation on Scalar-Tensor Gravity Theories
We show how observations of the perturbation spectra produced during
inflation may be used to constrain the parameters of general scalar-tensor
theories of gravity, which include both an inflaton and dilaton field. An
interesting feature of these models is the possibility that the curvature
perturbations on super-horizon scales may not be constant due to non-adiabatic
perturbations of the two fields. Within a given model, the tilt and relative
amplitude of the scalar and tensor perturbation spectra gives constraints on
the parameters of the gravity theory, which may be comparable with those from
primordial nucleosynthesis and post-Newtonian experiments.Comment: LaTeX (with RevTex) 19 pages, 8 uuencoded figures appended, also
available on WWW via http://star.maps.susx.ac.uk/index.htm
A Methodological Approach for Testing the Viability of Seeds Stored in Short-Term Seed Banks
[EN] Efficient management of `active¿ seed banks ¿ specifically aimed at the short-term storage at room temperature of seeds to be used locally in conservation/regeneration programmes of endemic or endangered plant species ¿ requires establishing the optimal storage time to maintain high seed viability, for each stored species. In this work, germination of seeds of the halophytes Thalictrum maritimum, Centaurea dracunculifolia and Linum maritimum has been investigated. The seeds had been stored for different periods of time in the seed bank of `La Albufera¿ Natural Park (Valencia, SE Spain) after collection in salt marshes of the Park, where small populations of the three species are present. Seeds of T. maritimum and C. dracunculifolia have a relatively short period of viability at room temperature, and should not be stored for more than three years. On the other hand, L. maritimum seeds maintain a high germination percentage and can be kept at room temperature for up to 10 years. T. maritimum seeds, in contrast to those of the other two species, did not germinate in in vitro tests nor when sown directly on a standard substrate, unless a pre-treatment of the seeds was applied, mechanical scarification being the most effective. These results will help to improve the management of the seed bank, to generate more efficiently new plants for reintroduction and reinforcement of populations of these species in their natural ecosystems within the Natural ParkForte Gil, J.; Yabor, L.; Bellido Nadal, A.; Collado Cerveró, F.; Ferrer-Gallego, P.; Vicente, O.; Boscaiu, M. (2017). A Methodological Approach for Testing the Viability of Seeds Stored in Short-Term Seed Banks. Notulae Scientia Biologicae. 9(4):563-570. doi:10.15835/nsb9410173S5635709
Black Hole Astrophysics in AdS Braneworlds
We consider astrophysics of large black holes localized on the brane in the
infinite Randall-Sundrum model. Using their description in terms of a conformal
field theory (CFT) coupled to gravity, deduced in Ref. [1], we show that they
undergo a period of rapid decay via Hawking radiation of CFT modes. For
example, a black hole of mass would shed most of its
mass in years if the AdS radius is mm,
currently the upper bound from table-top experiments. Since this is within the
mass range of X-ray binary systems containing a black hole, the evaporation
enhanced by the hidden sector CFT modes could cause the disappearance of X-ray
sources on the sky. This would be a striking signature of RS2 with a large AdS
radius. Alternatively, for shorter AdS radii, the evaporation would be slower.
In such cases, the persistence of X-ray binaries with black holes already
implies an upper bound on the AdS radius of L \la 10^{-2} mm, an order of
magnitude better than the bounds from table-top experiments. The observation of
primordial black holes with a mass in the MACHO range and an age comparable to the age of the universe would further
strengthen the bound on the AdS radius to L \la {\rm few} \times 10^{-6} mm.Comment: 14 pages, latex, no figures v2: added reference
Evidencias arqueológicas de desplomes paramentales traumáticos en las Termas Marítimas de Baelo Claudia. Reflexiones arqueosismológicas
Durante los años 2011 a 2013 se han localizado, identificado y excavado parcialmente los restos de un nuevo complejo termal en la ciudad hispanorromana de Baelo Claudia (Tarifa, Cádiz), situado en el suburbium occidental de la ciudad, junto a la línea de costa. Denominadas Termas Marítimas, construidas en la primera mitad del s. II d.C. y abandonadas en época de Diocleciano/Constantino han sido excavadas estratigráficamente con detalle, habiéndose detectado la existencia de fases anteriores (que se remontan al s. II a.C.) y una continuidad de uso del ambiente en época tardorromana y moderna, vinculada con la explotación de los recursos marinos. Especialmente singular ha sido la constatación del desplome traumático de parte de los paramentos de las habitaciones del edificio en dos momentos concretos: por un lado en la Antigüedad Tardía (500 d.C. circa), ya que una unidad muraria de una de las habitaciones (H-3), anexa a la natatio, se localizó completamente derrumbada sobre el suelo, conexionada; y por otro, el desplome del muro oeste de la natatio y el oriental de la cisterna, estructuras de más de seis metros de longitud y cuatro de altura mínima conservada, desplomadas sobre los niveles de abandono del asentamiento en época bajomedieval o moderna (ss. XIV-XV d.C.). Se trata en ambas ocasiones de colapsos estructurales no habituales en circunstancias normales en los procesos de sedimentación arqueológica, por lo que es muy probable que su desplome se pueda vincular con eventos sísmicos u otras causas naturales similare
RESULTADOS DE ENSAYOS DEL BANCO AUTOMÁTICO DE ASPERSORES
[ES] Desde el IFAPA Centro Chipiona como integrante del Sistema de Asesoramiento al
Regante de la Junta de Andalucía, se da servicio a las zonas del bajo Guadalquivir y
costeras de la provincia de Cádiz donde más profusamente se emplean los sistemas de
riego por aspersión. Las características del riego por aspersión y la variabilidad de su
eficiencia según las condiciones climáticas y de diseño, así como el alto número de
variables ajustables en el manejo, alimentaron la necesidad de crear un sistema con el que
ensayar el comportamiento de los diferentes aspersores frente a múltiples escenarios de
viento. El objeto último del ensayo es dar respuesta esta necesidad para ello se creó en el
IFAPA Centro Chipiona el primer banco automático de ensayo anemométrico de aspersores,
presentado en el XXXII Congreso Nacional de Riegos, mediante el cual se ensayan las
diferentes combinaciones de aspersión dentro de una matriz pluviométrica, tomándose
registro de las condiciones climáticas para crear posteriormente escenarios de modelado,
donde obtener la combinación de mayor eficiencia para las condiciones de diseño que se
planteen.Salvatierra Bellido, B.; Andrades Gonzalez, J.; Gómez Durán, E.; Viqueira Pina, S. (2015). RESULTADOS DE ENSAYOS DEL BANCO AUTOMÁTICO DE ASPERSORES. En XXXIII CONGRESO NACIONAL DE RIEGOS. Valencia 16-18 junio de 2015. Editorial Universitat Politècnica de València. https://doi.org/10.4995/CNRiegos.2015.1521OC
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