6,161 research outputs found
The Conformal Anomaly in General Rank 1 Symmetric Spaces and Associated Operator Product
We compute the one-loop effective action and the conformal anomaly associated
with the product of the Laplace type operators , acting in irreducible rank 1 symmetric spaces of non-compact
type. The explicit form of the zeta functions and the conformal anomaly of the
stress-energy momentum tensor is derived.Comment: 10 pages, LaTe
Constraints on the duality relation from ACT cluster data
The cosmic distance-duality relation (CDDR), , where and and are, respectively, the
luminosity and the angular diameter distances, holds as long as the number of
photons is conserved and gravity is described by a metric theory. Testing such
hypotheses is, therefore, an important task for both cosmology and fundamental
physics. In this paper we use 91 measurements of the gas mass fraction of
galaxy clusters recently reported by the Atacama Cosmology Telescope (ACT)
survey along with type Ia supernovae observations of the Union2.1 compilation
to probe a possible deviation from the value . Although in agreement
with the standard hyphothesis, we find that this combination of data tends to
favor negative values of which might be associated with some physical
processes increasing the number of photons and modifying the above relation to
.Comment: 4 pages, 2 figures, 2 table
Forms on Vector Bundles Over Compact Real Hyperbolic Manifolds
We study gauge theories based on abelian forms on real compact
hyperbolic manifolds. The tensor kernel trace formula and the spectral
functions associated with free generalized gauge fields are analyzed.Comment: Int. Journ. Modern Physics A, vol. 18 (2003), 2041-205
On Useful Conformal Tranformations In General Relativity
Local conformal transformations are known as a useful tool in various
applications of the gravitational theory, especially in cosmology. We describe
some new aspects of these transformations, in particular using them for
derivation of Einstein equations for the cosmological and Schwarzschild
metrics. Furthermore, the conformal transformation is applied for the
dimensional reduction of the Gauss-Bonnet topological invariant in to the
spaces of lower dimensions.Comment: 17 pages, LaTeX. The paper is intended mainly for pedagogical
purposes and represents a collection of exercises concerning local conformal
transformations and dimensional reduction. To be published in "Gravitation
and Cosmology
The anisotropic XY model on the inhomogeneous periodic chain
The static and dynamic properties of the anisotropic XY-model on
the inhomogeneous periodic chain, composed of cells with different
exchange interactions and magnetic moments, in a transverse field are
determined exactly at arbitrary temperatures. The properties are obtained by
introducing the Jordan-Wigner fermionization and by reducing the problem to a
diagonalization of a finite matrix of order. The quantum transitions are
determined exactly by analyzing, as a function of the field, the induced
magnetization 1/n\sum_{m=1}^{n}\mu_{m}\left ( denotes
the cell, the site within the cell, the magnetic moment at site
within the cell) and the spontaneous magnetization which is obtained from the correlations for large spin separations. These results,
which are obtained for infinite chains, correspond to an extension of the ones
obtained by Tong and Zhong(\textit{Physica B} \textbf{304,}91 (2001)). The
dynamic correlations, , and the dynamic
susceptibility, are also obtained at arbitrary
temperatures. Explicit results are presented in the limit T=0, where the
critical behaviour occurs, for the static susceptibility as
a function of the transverse field , and for the frequency dependency of
dynamic susceptibility .Comment: 33 pages, 13 figures, 01 table. Revised version (minor corrections)
accepted for publiction in Phys. Rev.
Femtocell deployment in LTE-A networks: A sustainability, economical and capacity analysis
Increasingly mobile data traffic and high quality service demand has driven standard developments and new mobile technologies deployment at an unprecedented level. Long Term Evolution (LTE) standard and its improved version LTE-Advanced (LTE-A) are two technology standards developed to cope with high levels of mobile data traffic demand. However, traffic and revenue disparity still is a reality, suggesting that traditional network deployment methods - based mainly on macro cellular sites - might prove to be cost ineffective in the long term. From another perspective, and increasingly important for mobile network operators, revenue is also a function of each mobile network deployment's sustainability. This work aims to comprehensively elaborate on those matters by presenting four specific scenarios with a comparative analysis of both macro and femtocell deployments (single and both technology networks). For each scenario, capacity, cost effectiveness and expected carbon emissions are the evaluated key indicators. This kind of analysis provides mobile networks operators with relevant information, enabling them to sustainably adapt business and provisioning models as well as network deployment strategies to current and future technological standards, while minimizing capital and operational expenditure (CAPEX/OPEX). The main contribution is that in short term, mixed macro and femtocell deployment scenarios are the most cost effective and sustainable option, while in mid to long term, as data traffic demand rises, femtocell deployments become the most sustainable, not only from economical and environmental points of view, but also from network coverage stand point.info:eu-repo/semantics/acceptedVersio
Economic and environmental comparative analysis on macro-femtocell deployments in LTE-A
This paper describes the economic and environmental comparative analysis performed on macro and femtocell
deployments and most prevalent results obtained. Four specific scenarios are studied and, for each one, an evaluation is made in terms of capacity, cost effectiveness and expected carbon emissions. It provides mobile networks operators (MNO) with relevant information, enabling them to adapt business models and deployment approaches to current and future trends in a sustainable way, while minimizing capital (CAPEX) and operation expenses (OPEX).info:eu-repo/semantics/acceptedVersio
Hybrid Model For Word Prediction Using Naive Bayes and Latent Information
Historically, the Natural Language Processing area has been given too much
attention by many researchers. One of the main motivation beyond this interest
is related to the word prediction problem, which states that given a set words
in a sentence, one can recommend the next word. In literature, this problem is
solved by methods based on syntactic or semantic analysis. Solely, each of
these analysis cannot achieve practical results for end-user applications. For
instance, the Latent Semantic Analysis can handle semantic features of text,
but cannot suggest words considering syntactical rules. On the other hand,
there are models that treat both methods together and achieve state-of-the-art
results, e.g. Deep Learning. These models can demand high computational effort,
which can make the model infeasible for certain types of applications. With the
advance of the technology and mathematical models, it is possible to develop
faster systems with more accuracy. This work proposes a hybrid word suggestion
model, based on Naive Bayes and Latent Semantic Analysis, considering
neighbouring words around unfilled gaps. Results show that this model could
achieve 44.2% of accuracy in the MSR Sentence Completion Challenge
Desenvolvimento inicial de espécies florestais em reflorestamento na região metropolitana do Rio de Janeiro.
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