2,853 research outputs found
Wind and the villages in Rincón de Ademuz, Spain
[EN] This study focuses on a sustainable system which makes it possible for the villages in the region of Rincón de Ademuz to have stood within their natural environment for over two thousand years. For this analysis the study has focused specifically on the wind factor. The dry weather and the wind trajectory make it possible to create a comfortable living environment in the villages. This research analyzed the position of a building unit in order to offer a clear representation of the relationship between wind and these villages.Ji, W.; Mileto, C.; Vegas López-Manzanares, F. (2022). Wind and the villages in Rincón de Ademuz, Spain. En Proceedings HERITAGE 2022 - International Conference on Vernacular Heritage: Culture, People and Sustainability. Editorial Universitat Politècnica de València. 111-117. https://doi.org/10.4995/HERITAGE2022.2022.1570211111
Power spectrum for the Bose-Einstein condensate dark matter
We assume that dark matter is composed of scalar particles that form a
Bose-Einstein condensate (BEC) at some point during the cosmic evolution.
Afterwards, cold dark matter is in the form of a condensate and behaves
slightly different from the standard dark matter component. We study the large
scale perturbative dynamics of the BEC dark matter in a model where this
component coexists with baryonic matter and cosmological constant. The
perturbative dynamics is studied using neo- Newtonian cosmology (where the
pressure is dynamically relevant for the homogeneous and isotropic background)
which is assumed to be correct for small values of the sound speed. We show
that BEC dark matter effects can be seen in the matter power spectrum if the
mass of the condensate particle lies in the range 15meV < m < 700meV leading to
a small, but perceptible, excess of power at large scales.Comment: 7 pages, 4 figures, Accepted for publication in Physics Letters
Newtonian Collapse of Scalar Field Dark Matter
In this letter, we develop a Newtonian approach to the collapse of galaxy
fluctuations of scalar field dark matter under initial conditions inferred from
simple assumptions. The full relativistic system, the so called
Einstein-Klein-Gordon, is reduced to the Schr\"odinger-Newton one in the weak
field limit. The scaling symmetries of the SN equations are exploited to track
the non-linear collapse of single scalar matter fluctuations. The results can
be applied to both real and complex scalar fields.Comment: 4 pages RevTex4 file, 4 eps figure
Evolution of the Schr\"odinger--Newton system for a self--gravitating scalar field
Using numerical techniques, we study the collapse of a scalar field
configuration in the Newtonian limit of the spherically symmetric
Einstein--Klein--Gordon (EKG) system, which results in the so called
Schr\"odinger--Newton (SN) set of equations. We present the numerical code
developed to evolve the SN system and topics related, like equilibrium
configurations and boundary conditions. Also, we analyze the evolution of
different initial configurations and the physical quantities associated to
them. In particular, we readdress the issue of the gravitational cooling
mechanism for Newtonian systems and find that all systems settle down onto a
0--node equilibrium configuration.Comment: RevTex file, 19 pages, 26 eps figures. Minor changes, matches version
to appear in PR
Aharonov-Bohm interferometry with quantum dots: scattering approach versus tunneling picture
We address the question of how to model electron transport through closed
Aharonov-Bohm interferometers which contain quantum dots. By explicitly
studying interferometers with one and two quantum dots, we establish the
connection between a tunneling-Hamiltonian formulation on the one hand and a
scattering-matrix approach on the other hand. We prove that, under certain
circumstances, both approaches are equivalent, i.e., both types of models can
describe the same experimental setups. Furthermore, we analyze how the
interplay of the Aharonov-Bohm phase and the orbital phase associated with the
lengths of the interferometers' arms affect transport properties.Comment: 8 pages, 8 figures, published versio
Chemical Bonding of Transition-metal Co Clusters with Graphene
We carried out density functional calculation to study Co clusters on
graphene. We deposit several free isomers in different disposition respect to
hexagonal lattice nodes, studying even the isomer recently obtained
as the most stable one. Surprisingly, Co clusters bonded to graphene
prefer structures where the low lying isomer is much
distorted, because it is linked with more bonds than in previous works. For any
isomer the most stable position binds to graphene by the Co atoms that can lose
electrons. We find that the charge transfers between graphene and clusters are
small enough to conclude that the Co-graphene binding is not ionic-like but
chemical. Besides, the same order of stability among the different isomers on
doped graphene is well kept. These findings could also be of interest for
magnetic clusters on graphenic nanostructures such as ribbons and nanotubes.Comment: 12 pages, 6 figure
as Dark Matter
In this paper we consider scalar field potential as a candidate to
dark matter. If it is an ultralight boson particle, it condensates like a
Bose-Einstein system at very early times and forms the basic structure of the
Universe. Real scalar fields collapse in equilibrium configurations that
oscillate in space-time (oscillatons).The cosmological behavior of the field
equations are solved using the dynamical system formalism. We use the current
cosmological parameters as constraints for the present value of the scalar
field. We reproduce the cosmological predictions of the standard CDM
model with this model. Therefore, scalar field dark matter seems to be a good
alternative to cold dark matter nature.Comment: Accepted for publication in MNRAS 11 pages, 7 figure
Are galaxies extending?
It is suggested that the recently observed size evolution of very massive
compact galaxies in the early universe can be explained, if dark matter is in
Bose Einstein condensate.
In this model the size of the dark matter halos and galaxies depends on the
correlation length of dark matter and, hence, on the the expansion of the
universe. This theory predicts that the size of the galaxies increases as the
Hubble radius of the universe even without merging, which agrees well with the
recent observational data.Comment: 5 pages, 2figs, revtex,accepted version for PL
- …