4,128 research outputs found
Critical behavior of 3D Z(N) lattice gauge theories at zero temperature
Three-dimensional lattice gauge theories at zero temperature are
studied for various values of . Using a modified phenomenological
renormalization group, we explore the critical behavior of the generalized
model for . Numerical computations are used to simulate
vector models for for lattices with linear extension up
to . We locate the critical points of phase transitions and establish
their scaling with . The values of the critical indices indicate that the
models with belong to the universality class of the three-dimensional
model. However, the exponent derived from the heat capacity is
consistent with the Ising universality class. We discuss a possible resolution
of this puzzle. We also demonstrate the existence of a rotationally symmetric
region within the ordered phase for all at least in the finite
volume.Comment: 25 pages, 4 figures, 8 table
A Variational Formulation of Symplectic Noncommutative Mechanics
The standard lore in noncommutative physics is the use of first order
variational description of a dynamical system to probe the space
noncommutativity and its consequences in the dynamics in phase space. As the
ultimate goal is to understand the inherent space noncommutativity we propose a
variational principle for noncommutative dynamical systems in configuration
space, based on results of our previous work [14]. We hope that this
variational formulation in configuration space can be of help to elucidate the
definition of some global and dynamical properties of classical and quantum
noncommutative space.Comment: 17 pages, Latex. Accepted for publication in IJGMM
To what extent can the experience of outdoor learning contexts prevent permanent school exclusion for older learners? A visual analysis
This is the author accepted manuscript. The final version is available from IATED via the DOI in this record.We report on a one-year project that focused on outdoor learning experiences for learners 12 - 14 years of age in a woodland environment in the UK. We wanted to investigate the ways in which experience in the outdoor environment could potentially mitigate school factors such as practitioner values and attitudes, learner motivation and engagement [1] that contribute to the processes of permanent school exclusion and therefore examine the claim that outdoor learning could provide an ‘alternative’ to using exclusion as a disciplinary sanction [2]. Permanent school exclusion has been rising in the UK since 2014 and the number of permanent exclusions in England in 2016 rose from 6,685 to 7,720 pupils in 2017 [3] and it is particularly prevalent in the age group involved in this project. While some argue that outdoor learning is often evangelised as a panacea for the shortcomings of school environments, particularly for very young learners [4], we draw on the work presented in [5] to make a case for the ways in which outdoor experiences can contribute to the learning needs of older learners at risk of permanent exclusion. We analysed a sample of 102 photographs taken by the project team during the practical sessions in the woodland. We devised a set of categories for coding the images based on our theoretical and pedagogical concerns, and from our reading of empirical literature. Two members of the project team tried out our initial coding categories with the sample in order to check for exhaustiveness and exclusivity, and to try and avoid overlap of codes [6]. Photographs were then coded independently by the four members of the project team using the agreed coding framework. We ask critical questions about the ways in which space, risk, resources, outdoor pedagogies and adult identities can be mobilised to support the learning needs of young people who find school a difficult place to be. In this presentation we will use a selection of photographs to demonstrate that our approach to Visual Content Analysis, drawing on [6] in using a methodologically explicit approach to analysing visual evidence, can produce results that are valid and theoretically ‘interesting’. We interpret the implications of our analysis for educational professionals who want to learn more about preventing permanent exclusion
The selective effect of environment on the atomic and molecular gas-to-dust ratio of nearby galaxies in the Herschel Reference Survey
We combine dust, atomic (HI) and molecular (H) hydrogen mass
measurements for 176 galaxies in the Herschel Reference Survey to investigate
the effect of environment on the gas-to-dust mass ()
ratio of nearby galaxies. We find that, at fixed stellar mass, the average
ratio varies by no more than a factor of 2
when moving from field to cluster galaxies, with Virgo galaxies being slightly
more dust rich (per unit of gas) than isolated systems. Remarkably, once the
molecular and atomic hydrogen phases are investigated separately, we find that
\hi-deficient galaxies have at the same time lower
ratio but higher ratio than \hi-normal systems. In
other words, they are poorer in atomic but richer in molecular hydrogen if
normalized to their dust content. By comparing our findings with the
predictions of theoretical models, we show that the opposite behavior observed
in the and ratios is
fully consistent with outside-in stripping of the interstellar medium (ISM),
and is simply a consequence of the different distribution of dust, \hi\ and
H across the disk. Our results demonstrate that the small environmental
variations in the total ratio, as well as in the
gas-phase metallicity, do not automatically imply that environmental mechanisms
are not able to affect the dust and metal content of the ISM in galaxies.Comment: 11 pages, 6 figures, 2 tables. Accepted for publication in MNRA
The bolometric and UV attenuation in normal spiral galaxies of the Herschel Reference Survey
The dust in nearby galaxies absorbs a fraction of the
UV-optical-near-infrared radiation produced by stars. This energy is
consequently re-emitted in the infrared. We investigate the portion of the
stellar radiation absorbed by spiral galaxies from the HRS by modelling their
UV-to-submillimetre spectral energy distributions. Our models provide an
attenuated and intrinsic SED from which we find that on average 32 % of all
starlight is absorbed by dust. We define the UV heating fraction as the
percentage of dust luminosity that comes from absorbed UV photons and find that
this is 56 %, on average. This percentage varies with morphological type, with
later types having significantly higher UV heating fractions. We find a strong
correlation between the UV heating fraction and specific star formation rate
and provide a power-law fit. Our models allow us to revisit the IRX-AFUV
relations, and derive these quantities directly within a self-consistent
framework. We calibrate this relation for different bins of NUV-r colour and
provide simple relations to relate these parameters. We investigated the
robustness of our method and we conclude that the derived parameters are
reliable within the uncertainties which are inherent to the adopted SED model.
This calls for a deeper investigation on how well extinction and attenuation
can be determined through panchromatic SED modelling.Comment: 14 pages, 7 figures. Accepted for publication in Astronomy &
Astrophysic
Effect of decreasing dietary crude protein on growth performance, feed efficiency and meat quality of finishing Charolais bulls
This study aimed to evaluate the effect of decreasing dietary crude protein (CP) on the performance of finishing Charolais bulls in the Italian rearing system. Animals were fed two diets, differing only in the CP level (low protein (LP), 13.5% CP versus control (CON), 15.0% CP). Dry matter (DM) intake (DMI) and animals\u2019 weights were recorded to obtain average daily gain (ADG) and feed conversion rate (FCR). Feed and fecal samples were collected to evaluate digestibility of diet components. Daily cost of the ration (DRC), feed cost per kg of daily weight gain (CDG) and daily gross margin (DGM) were calculated to analyze the possible benefits of decreasing the protein level. Meat quality analyses were also conducted. Higher DMI (10.6 versus 10 kg/d; p < 0.05) and ADG (1.47 versus 1.36 kg/d; p < 0.05) were observed for CON. No differences in FCR or digestibility were found. Even if the DRC was lower (p < 0.05) for the LP diet (2.26 versus 1.97 \u20ac; CON versus LP), no difference was reported for CDG and DGM. Meat lightness and redness were significantly lower and higher in the LP, respectively. To conclude, the CP requirement in these rearing conditions appeared to be higher than 13.5%
Relativistic Runge-Lenz vector: from SYM to SO(4) scalar field theory
Starting from SYM and using an appropriate Higgs mechanism we
reconsider the construction of a scalar field theory non-minimally coupled to a
Coulomb potential with a relativistic SO(4) symmetry and check for scalar field
consistency conditions. This scalar field theory can also be obtained from a
relativistic particle Lagrangian with a proper implementation of the
non-minimal coupling. We provide the generalization of the non-relativistic
construction of the Runge-Lenz vector to the relativistic case and show
explicitly that this new vector generates the SO(4) algebra. Using the power of
the SO(4) symmetry, we calculate the relativistic hydrogen atom spectrum. We
provide a generalization of the Kustaanheimo-Stiefel transformation to the
relativistic case and relate our results with the corresponding relativistic
oscillator. Finally, in the light of these results, we reconsider the
calculation of the hydrogen atom spectrum from the cusp anomalous dimension
given in [2].Comment: 17 pages. Enhaced version matching the published JHEP version. Typos
corrected. The argument of concistence at the end of section 2 was correcte
Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales
[abridged]
Aims. The aim of the present paper is to provide new and more detailed
relations at the kpc scale between the gas surface density and the face-on
optical depth directly calibrated on galaxies, in order to compute the
attenuation not only for semi-analytic models but also observationally as new
and upcoming radio observatories are able to trace gas ever farther in the
Universe.
Methods. We have selected a sample of 4 nearby resolved galaxies and a sample
of 27 unresolved galaxies from the Herschel Reference Survey and the Very
Nearby Galaxies Survey, for which we have a large set of multi-wavelength data
from the FUV to the FIR including metallicity gradients for resolved galaxies,
along with radio HI and CO observations. For each pixel in resolved galaxies
and for each galaxy in the unresolved sample, we compute the face-on optical
depth from the attenuation determined with the CIGALE SED fitting code and an
assumed geometry. We determine the gas surface density from HI and CO
observations with a metallicity-dependent XCO factor.
Results. We provide new, simple to use, relations to determine the face-on
optical depth from the gas surface density, taking the metallicity into
account, which proves to be crucial for a proper estimate. The method used to
determine the gas surface density or the face-on optical depth has little
impact on the relations except for galaxies that have an inclination over 50d.
Finally, we provide detailed instructions on how to compute the attenuation
practically from the gas surface density taking into account possible
information on the metallicity.
Conclusions. Examination of the influence of these new relations on simulated
FUV and IR luminosity functions shows a clear impact compared to older oft-used
relations, which in turn could affect the conclusions drawn from studies based
on large scale cosmological simulations.Comment: 24 pages, 21 figures, accepted for publication in A&
The Arecibo Galaxy Environment Survey: II. A HI view of the Abell cluster 1367 and its outskirts
We present 21 cm HI line observations of 5x1 square degrees centered on the
local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment
Survey. One hundred sources are detected (79 new HI measurements and 50 new
redshifts), more than half belonging to the cluster core and its infalling
region. Combining the HI data with SDSS optical imaging we show that our HI
selected sample follows scaling relations similar to the ones usually observed
in optically selected samples. Interestingly all galaxies in our sample appear
to have nearly the same baryon fraction independently of their size, surface
brightness and luminosity. The most striking difference between HI and
optically selected samples resides in their large scale distribution: whereas
optical and X-ray observations trace the cluster core very well, in HI there is
almost no evidence of the presence of the cluster. Some implications on the
determination of the cluster luminosity function and HI distribution for
samples selected at different wavelength are also discussed.Comment: 22 pages, 15 figures, 4 tables. Accepted for publication on MNRAS
Main Journal. High resolution version of this paper can be downloaded at
http://www.astro.cf.ac.uk/pub/Luca.Cortese/papers/ages_a1367.pdf . Datacubes
and catalogs can be downloaded at http://www.naic.edu/~ages/public_data.htm
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