19 research outputs found
The Horizon-AGN simulation: evolution of galaxy properties over cosmic time
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We compare the predictions of Horizon-AGN, a hydro-dynamical cosmological simulation that uses an adaptive mesh refinement code, to observational data in the redshift range 0 < z < 6. We study the reproduction, by the simulation, of quantities that trace the aggregate stellar-mass growth of galaxies over cosmic time: luminosity and stellar-mass functions, the star formation main sequence, rest-frame UV-optical-near infrared colours and the cosmic star-formation history. We show that Horizon-AGN, which is not tuned to reproduce the local Universe, produces good overall agreement with these quantities, from the present day to the epoch when the Universe was 5% of its current age. By comparison to Horizon-noAGN, a twin simulation without AGN feedback, we quantify how feedback from black holes is likely to help shape galaxy stellar-mass growth in the redshift range 0 < z < 6, particularly in the most massive galaxies. Our results demonstrate that Horizon-AGN successfully captures the evolutionary trends of observed galaxies over the lifetime of the Universe, making it an excellent tool for studying the processes that drive galaxy evolution and making predictions for the next generation of galaxy surveys.Peer reviewedFinal Published versio
Non-extremal Localised Branes and Vacuum Solutions in M-Theory
Non-extremal overlapping p-brane supergravity solutions localised in their
relative transverse coordinates are constructed. The construction uses an
algebraic method of solving the bosonic equations of motion. It is shown that
these non-extremal solutions can be obtained from the extremal solutions by
means of the superposition of two deformation functions defined by vacuum
solutions of M-theory. Vacuum solutions of M-theory including irrational powers
of harmonic functions are discussed.Comment: LaTeX, 16 pages, no figures, typos correcte
Inflation on an Open Racetrack
We present a variant of warped D-brane inflation by incorporating multiple
sets of holomorphically-embedded D7-branes involved in moduli stabilization
with extent into a warped throat. The resultant D3-brane motion depends on the
D7-brane configuration and the relative position of the D3-brane in these
backgrounds. The non-perturbative moduli stabilization superpotential takes the
racetrack form, but the additional D3-brane open string moduli dependence
provides more flexibilities in model building. For concreteness, we consider
D3-brane motion in the warped deformed conifold with the presence of multiple
D7-branes, and derive the scalar potential valid for the entire throat. By
explicit tuning of the microphysical parameters, we obtain inflationary
trajectories near an inflection point for various D7-brane configurations.
Moreover, the open racetrack potential admits approximate Minkowski vacua
before uplifting. We demonstrate with a concrete D-brane inflation model where
the Hubble scale during inflation can exceed the gravitino mass. Finally, the
multiple sets of D7-branes present in this open racetrack setup also provides a
mechanism to stabilize the D3-brane to metastable vacua in the intermediate
region of the warped throat.Comment: 29 pages, 15 figures, pre-print number and references adde
The scalar and pseudoscalar sector in a five-dimensional approach to chiral symmetry breaking
Premi a l'excel·lĂšncia investigadora. Ămbit de les CiĂšncies Experimentals. 2008We study the scalar and pseudoscalar sector in a five-dimenional model describing chiral symmetry breaking. We calculate the scalar and pseudoscalar two-point correlator, the mass spectrum and interactions. We also obtain the scalar and pseudoscalar contributions to the coefficients of the chiral lagrangian and determine the scalar form factor of the pseudo-Goldstone bosons. Most quantities show a good agreement with QC
Type IIB orientifolds on Gepner points
We study various aspects of orientifold projections of Type IIB closed string
theory on Gepner points in different dimensions. The open string sector is
introduced, in the usual constructive way, in order to cancel RR charges
carried by orientifold planes. Moddings by cyclic permutations of the internal
N=2 superconformal blocks as well as by discrete phase symmetries are
implemented. Reduction in the number of generations, breaking or enhancements
of gauge symmetries and topology changes are shown to be induced by such
moddings. Antibranes sector is also considered; in particular we show how non
supersymmetric models with antibranes and free of closed and open tachyons do
appear in this context. A systematic study of consistent models in D=8
dimensions and some illustrative examples in D=6 and D=4 dimensions are
presented.Comment: 67 pages, no figures References added, typos correcte
Theory and Phenomenology of Type I strings and M-theory
The physical motivations and the basic construction rules for Type I strings
and M-theory compactifications are reviewed in light of the recent
developments. The first part contains the basic theoretical ingredients needed
for building four-dimensional supersymmetric models, models with broken
supersymmetry and for computing low-energy actions and quantum corrections to
them. The second part contains some phenomenological applications to brane
world scenarios with low values of the string scale and large extra dimensions.Comment: 129 pages, 7 eps figures, LaTeX, version to appear in Class. Quantum
Gra
W Plus Heavy Quark Production at the Tevatron
We summarize the motivations for and the status of the calculation of the heavy quark production process in colliders to Next-to-Leading Order in QCD. This process can be used to constrain the strange quark distribution function at high at the Tevatron, and also to study the bottom content of ~jet events. In addition, when crossed, the calculation essentially describes the single top quark production process to Next-to-Leading Order in QCD
The Horizon-AGN simulation: evolution of galaxy properties over cosmic time
We compare the predictions of Horizon-AGN, a hydro-dynamical cosmological simulation that uses an adaptive mesh refinement code, to observational data in the redshift range 0<z<6. We study the reproduction, by the simulation, of quantities that trace the aggregate stellar-mass growth of galaxies over cosmic time: luminosity and stellar-mass functions, the star formation main sequence, rest-frame UV-optical-near infrared colours and the cosmic star-formation history. We show that Horizon-AGN, which is not tuned to reproduce the local Universe, produces good overall agreement with these quantities, from the present day to the epoch when the Universe was 5% of its current age. By comparison to Horizon-noAGN, a twin simulation without AGN feedback, we quantify how feedback from black holes is likely to help shape galaxy stellar-mass growth in the redshift range 0<z<6, particularly in the most massive galaxies. Our results demonstrate that Horizon-AGN successfully captures the evolutionary trends of observed galaxies over the lifetime of the Universe, making it an excellent tool for studying the processes that drive galaxy evolution and making predictions for the next generation of galaxy surveys
Constraining the Dense Matter Equation of State with Joint Analysis of NICER and LIGO/Virgo Measurements
The NICER collaboration recently published a joint estimate of the mass and the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling. In Raaijmakers et al. (2019) the implications of this measurement for the dense matter equation of state (EOS) were explored using two parameterizations of the high-density EOS: a piecewise-polytropic model, and a model based on the speed of sound in neutron stars. In this work we obtain further constraints on the EOS following this approach, but we also include information about the tidal deformability of neutron stars from the gravitational wave signal of the compact binary merger GW170817. We compare the constraints on the EOS to those set by the recent measurement of a 2.14 solar mass pulsar, included as a likelihood function approximated by a Gaussian, and find a small increase in information gain. To show the flexibility of our method, we also explore the possibility that GW170817 was a neutron star-black hole merger, which yields weaker constraints on the EOS