17,056 research outputs found
Holographic phase transitions from higgsed, non abelian charged black holes
We find solutions of a gravity-Yang-Mills-Higgs theory in four dimensions
that represent asymptotic anti-de Sitter charged black holes with partial/full
gauge symmetry breaking. We then apply the AdS/CFT correspondence to study the
strong coupling regime of a quantum field theory at temperature and
finite chemical potential, which undergoes transitions to phases exhibiting the
condensation of a composite charged vector operator below a critical
temperature , presumably describing -wave superconductors. In the
case of -wave superconductors the transitions are always of second order.
But for -wave superconductors we determine the existence of a critical value
of the gravitational coupling (for fixed Higgs v.e.v. parameter
) beyond which the transitions become of first order. As a
by-product, we show that the -wave phase is energetically favored over the
one, for any values of the parameters. We also find the ground state
solutions corresponding to zero temperature. Such states are described by
domain wall geometries that interpolate between spaces with different
light velocities, and for a given , they exist below a critical
value of the coupling. The behavior of the order parameter as function of the
gravitational coupling near the critical coupling suggests the presence of
second order quantum phase transitions. We finally study the dependence of the
solution on the Higgs coupling, and find the existence of a critical value
beyond which no condensed solution is present.Comment: 29 pages, 43 figure
Scaling relations of the colour-detected cluster RzCS 052 at z=1.016 and of some other high redshift clusters
We report on the discovery of the z=1.016 cluster RzCS 052 using a modified
red sequence method, followup spectroscopy and X-ray imaging. This cluster has
a velocity dispersion of 710+-150 km/s, a virial mass of 4.0e14 Msol (based on
21 spectroscopically confirmed members) and an X-ray luminosity of (0.68+-
0.47)e44 ergs/s in the [1-4] keV band. This optically selected cluster appears
to be of richness class 3 and to follow the known L_X-sigma_v relation for high
redshift X-ray selected clusters. Using these data, we find that the halo
occupation number for this cluster is only marginally consistent with what
expected assuming a self-similar evolution of cluster scaling relations,
suggesting perhaps a break of them at z~1. We also rule out a strong galaxy
merging activity between z=1 and today. Finally, we present a Bayesian approach
to measuring cluster velocity dispersions and X-ray luminosities in the
presence of a background: we critically reanalyze recent claims for X-ray
underluminous clusters using these techniques and find that the clusters can be
accommodated within the existing L_X -sigma_v relation.Comment: MNRAS, in pres
Results of the 2010 Mathematical Contest in Modeling
Modeling ForumA total of 2,254 teams of undergraduates from hundreds of institutions and
departments in 14 countries, spent a weekend in February working on applied
mathematicsproblems inthe 26thMathematicalContest inModeling(MCM)!R .
The 2010MCMbegan at 8:00 P.M. EST on Thursday, February 18, and ended
at 8:00 P.M. EST on Monday, February 22. During that time, teams of up to
three undergraduates researched, modeled, and submitted a solution to one
of two open-ended modeling problems. Students registered, obtained contest
materials, downloaded the problem and data, and entered completion data
through COMAP’s MCM Website. After a weekend of hard work, solution
papers were sent to COMAP on Monday. Two of the top papers appear in this
issue of The UMAP Journal, together with commentaries
Non-user benefits emanating from enhanced water flow to the Yala Protected Area Complex
Water is a multiple use resource. Increasing scarcity and competition from various sectors is an important dimension to be considered in its management. Understanding the value of water to different water uses is, therefore, necessary to assist decision-making in water allocation among sectors. Although water used in agriculture can be valued using production function approaches, such direct valuation methods are not available for the environmental uses of water. This paper uses non-market valuation methods to estimate the economic value of a committed flow through a unique ecosystem, the Yala Protected Area Complex (YPC). The Yala Protected Area Complex is an important wildlife refuge situated in south-eastern Sri Lanka. Its large land extent, undisturbed nature, and abundance and diversity of fauna contribute to its uniqueness. The fact that the YPC is also the most visited national park in Sri Lanka is partially a result of this uniqueness. However, maintenance of the park’s ecosystem depends on the flow of the Menik Ganga. This flow is regulated by the Veheragala Reservoir Project, and there is now discussion of reducing flow into the park by about half of the current level. The proposed plan ensures dry season flow into the YPC and, therefore, has been deemed acceptable. However, there is a possibility that farmers will demand further water releases during the dry season which could in turn endanger the planned downstream water releases. So there is a potential trade-off between environmental and irrigation uses of water. A willingness to pay (WTP) survey was conducted in ten districts in Sri Lanka during the fourth quarter of 2008 to estimate the WTP of the general population of the country towards maintaining this important environmental resource. In the hypothetical market presented, participants were told of the need for financial contributions from the general public to ensure the release of a minimum downstream flow commitment of 50 MCM. Participants were also informed of how this flow would enhance the ecosystem of the YPC. A single bound dichotomous choice contingent valuation approach was used as the elicitation format. Nonobligatory voluntary contributions were solicited towards a trust fund that could be used to ensure release of the required quantity of water downstream during dry months. According to the results of a binary logistic regression, income, age, and religious attachments are important factors affecting the decision to contribute to environmental flow maintenance to the YPC. Sixty-five percent of respondents were willing to pay something to ensure the maintenance of an adequate environmental flow in the YPC. The estimated mean WTP for water releases to enhance the YPC is Sri Lankan Rupees (SLR) 435 per year. Over the requested payment horizon of 10 years, the present value of aggregate WTP from the Sri Lankan population to enhance the ecosystem of the YPC is SLR 12 billion. This quantity greatly surpasses the present value of net benefits from rice farming estimated at SLR 0.64 billion, which would be generated if the same quantity of water was used for irrigation for 10 years (assuming current prices and input intensities). Thus, there is a clear opportunity for national welfare gain by ensuring adequate flow in YPC.Length: pp.37-47Water useMultiple useWildlifeHabitatsEcosystemsIrrigation waterWater allocation
IIR Adaptive Filters for Detection of Gravitational Waves from Coalescing Binaries
In this paper we propose a new strategy for gravitational waves detection
from coalescing binaries, using IIR Adaptive Line Enhancer (ALE) filters. This
strategy is a classical hierarchical strategy in which the ALE filters have the
role of triggers, used to select data chunks which may contain gravitational
events, to be further analyzed with more refined optimal techniques, like the
the classical Matched Filter Technique. After a direct comparison of the
performances of ALE filters with the Wiener-Komolgoroff optimum filters
(matched filters), necessary to discuss their performance and to evaluate the
statistical limitation in their use as triggers, we performed a series of
tests, demonstrating that these filters are quite promising both for the
relatively small computational power needed and for the robustness of the
algorithms used. The performed tests have shown a weak point of ALE filters,
that we fixed by introducing a further strategy, based on a dynamic bank of ALE
filters, running simultaneously, but started after fixed delay times. The
results of this global trigger strategy seems to be very promising, and can be
already used in the present interferometers, since it has the great advantage
of requiring a quite small computational power and can easily run in real-time,
in parallel with other data analysis algorithms.Comment: Accepted at SPIE: "Astronomical Telescopes and Instrumentation". 9
pages, 3 figure
Non-user benefits emanating from enhanced water flow to Yala Protected Area Complex. Abstract only
EcosystemsWater resource managementMultiple useDecision makingWater allocationEnvironmental flows
Consistency of Bayesian inference with Gaussian process priors in an elliptic inverse problem
For a bounded domain in and a given smooth
function , we consider the statistical nonlinear
inverse problem of recovering the conductivity in the divergence form
equation from discrete noisy point
evaluations of the solution on . We study the statistical
performance of Bayesian nonparametric procedures based on a flexible class of
Gaussian (or hierarchical Gaussian) process priors, whose implementation is
feasible by MCMC methods. We show that, as the number of measurements
increases, the resulting posterior distributions concentrate around the true
parameter generating the data, and derive a convergence rate for the reconstruction error of the associated posterior means, in
-distance
Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm
In this article we study the classical nearest-neighbour spin-ice model
(nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm.
The nnSI describes several of the salient features of the spin-ice materials.
Despite its simplicity it exhibits a remarkably rich behaviour. The model has
been studied using a variety of techniques, thus it serves as an ideal
benchmark to test the capabilities of the Wang Landau algorithm in magnetically
frustrated systems. We study in detail the residual entropy of the nnSI and, by
introducing an applied magnetic field in two different crystallographic
directions ([111] and [100],) we explore the physics of the kagome-ice phase,
the transition to full polarisation, and the three dimensional Kasteleyn
transition. In the latter case, we discuss how additional constraints can be
added to the Hamiltonian, by taking into account a selective choice of states
in the partition function and, then, show how this choice leads to the
realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure
A principled and cosmopolitan neuroethics: considerations for international relevance
Neuroethics applies cognitive neuroscience for prescribing alterations to conceptions of self and society, and for prescriptively judging the ethical applications of neurotechnologies. Plentiful normative premises are available to ground such prescriptivity, however prescriptive neuroethics may remain fragmented by social conventions, cultural ideologies, and ethical theories. Herein we offer that an objectively principled neuroethics for international relevance requires a new meta-ethics: understanding how morality works, and how humans manage and improve morality, as objectively based on the brain and social sciences. This new meta-ethics will simultaneously equip neuroethics for evaluating and revising older cultural ideologies and ethical theories, and direct neuroethics towards scientifically valid views of encultured humans intelligently managing moralities. Bypassing absolutism, cultural essentialisms, and unrealistic ethical philosophies, neuroethics arrives at a small set of principles about proper human flourishing that are more culturally inclusive and cosmopolitan in spirit. This cosmopolitanism in turn suggests augmentations to traditional medical ethics in the form of four principled guidelines for international consideration: empowerment, non-obsolescence, self-creativity, and citizenship
Naturalizing Neuroethics? A Syncretic Approach
Neuroethics is uniquely situated to socially interpret what brain sciences are learning about social and moral cognition while helping society hold neuroscientific research and neurotechnological applications to firm moral standards. Both tasks, if they are to be pursued successfully, must find ways to closely relate the “neuro” with the “ethical.” Keeping them apart has been the objective of nonnaturalist worldviews worried about scientism and reductionism, and now they complain about “neuroessentialism” and similar labels for dissolutions of agency and responsibility into mere brain activity. A nonnaturalistic neuroethics, on whatever metaphysical basis, insists that the biology of brains could not explain moral decisions or ground moral norms. We agree on that much, since the methodology of brain sciences presumes, and cannot replace, behavioral and psychological attributions of moral capacity and conduct. But the social and the neurological are always related through the anthropological; and that common basis is, not coincidentally, also where the ethical is grounded, as humanity upholds persons as bearers of moral worth and moral capacity. Neuroethics, by focusing on persons, need never resort to nonnaturalism to uphold what ultimately matters for ethics, and “naturalizing” neuroethics is also unnecessary for a humanity-centered neurobioethics
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