4,949 research outputs found
Generalized Non-Commutative Inflation
Non-commutative geometry indicates a deformation of the energy-momentum
dispersion relation for massless particles.
This distorted energy-momentum relation can affect the radiation dominated
phase of the universe at sufficiently high temperature. This prompted the idea
of non-commutative inflation by Alexander, Brandenberger and Magueijo (2003,
2005 and 2007). These authors studied a one-parameter family of
non-relativistic dispersion relation that leads to inflation: the
family of curves . We show here how the
conceptually different structure of symmetries of non-commutative spaces can
lead, in a mathematically consistent way, to the fundamental equations of
non-commutative inflation driven by radiation. We describe how this structure
can be considered independently of (but including) the idea of non-commutative
spaces as a starting point of the general inflationary deformation of
. We analyze the conditions on the dispersion relation that
leads to inflation as a set of inequalities which plays the same role as the
slow roll conditions on the potential of a scalar field. We study conditions
for a possible numerical approach to obtain a general one parameter family of
dispersion relations that lead to successful inflation.Comment: Final version considerably improved; Non-commutative inflation
rigorously mathematically formulate
A conceptual problem for non-commutative inflation and the new approach for non-relativistic inflationary equation of state
In a previous paper, we connected the phenomenological non-commutative
inflation of Alexander, Brandenberger and Magueijo (2003) and Koh S and
Brandenberger (2007) with the formal representation theory of groups and
algebras and analyzed minimal conditions that the deformed dispersion relation
should satisfy in order to lead to a successful inflation. In that paper, we
showed that elementary tools of algebra allow a group like procedure in which
even Hopf algebras (roughly the symmetries of non-commutative spaces) could
lead to the equation of state of inflationary radiation. In this paper, we show
that there exists a conceptual problem with the kind of representation that
leads to the fundamental equations of the model. The problem comes from an
incompatibility between one of the minimal conditions for successful inflation
(the momentum of individual photons is bounded from above) and the group
structure of the representation which leads to the fundamental inflationary
equations of state. We show that such a group structure, although
mathematically allowed, would lead to problems with the overall consistency of
physics, like in scattering theory, for example. Therefore, it follows that the
procedure to obtain those equations should be modified according to one of two
possible proposals that we consider here. One of them relates to the general
theory of Hopf algebras while the other is based on a representation theorem of
Von Neumann algebras, a proposal already suggested by us to take into account
interactions in the inflationary equation of state. This reopens the problem of
finding inflationary deformed dispersion relations and all developments which
followed the first paper of Non-commutative Inflation.Comment: Phys. Rev. D, 2013, in pres
The Brazilian grape germplasm bank: phenology and resistance to main fungal diseases.
In recent years viticulture has reached a very important role in Brazilian fruit production, not only in temperate zones, but also as an altemative for tropical regions. These different climates require cultivars with wide-ranging production cycles.Resumo P-60
Quantum state-dependent diffusion and multiplicative noise: a microscopic approach
The state-dependent diffusion, which concerns the Brownian motion of a
particle in inhomogeneous media has been described phenomenologically in a
number of ways. Based on a system-reservoir nonlinear coupling model we present
a microscopic approach to quantum state-dependent diffusion and multiplicative
noise in terms of a quantum Markovian Langevin description and an associated
Fokker-Planck equation in position space in the overdamped limit. We examine
the thermodynamic consistency and explore the possibility of observing a
quantum current, a generic quantum effect, as a consequence of this
state-dependent diffusion similar to one proposed by B\"{u}ttiker [Z. Phys. B
{\bf 68}, 161 (1987)] in a classical context several years ago.Comment: To be published in Journal of Statistical Physics 28 pages, 3 figure
Adaptability and stability of genotypes of sweet sorghum by GGEBiplot and Toler methods.
Sweet sorghum has considerable potential for ethanol and energy production. The crop is adaptable and can be grown under a wide range of cultivation conditions in marginal areas; however, studies of phenotypic stability are lacking under tropical conditions. Various methods can be used to assess the stability of the crop. Some of these methods generate the same basic information, whereas others provide additional information on genotype x environment (G x E) interactions and/or a description of the genotypes and environments. In this study, we evaluated the complementarity of two methods, GGEBiplot and Toler, with the aim of achieving more detailed information on G x E interactions and their implications for selection of sweet sorghum genotypes. We used data from 25 sorghum genotypes grown in different environments and evaluated the following traits: flowering (FLOW), green mass yield (GMY), total soluble solids (TSS), and tons of Brix per hectare (TBH). Significant G x E interactions were found for all traits. The most stable genotypes identified with the GGEBiplot method were CMSXS643 for FLOW, CMSXS644 and CMSXS647 for GMY, CMSXS646 and CMSXS637 for TSS, and BRS511 and CMSXSS647 for TBH. Especially for TBH, the genotype BRS511 was classified as doubly desirable by the Toler method; however, unlike the result of the GGEBiplot method, the genotype CMSXS647 was also found to be doubly undesirable. The two analytical methods were complementary and enabled a more reliable identification of adapted and stable genotypes
Photoproduction at collider energies: from RHIC and HERA to the LHC
We present the mini-proceedings of the workshop on ``Photoproduction at
collider energies: from RHIC and HERA to the LHC'' held at the European Centre
for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Trento)
from January 15 to 19, 2007. The workshop gathered both theorists and
experimentalists to discuss the current status of investigations of high-energy
photon-induced processes at different colliders (HERA, RHIC, and Tevatron) as
well as preparations for extension of these studies at the LHC. The main
physics topics covered were: (i) small- QCD in photoproduction studies with
protons and in electromagnetic (aka. ultraperipheral) nucleus-nucleus
collisions, (ii) hard diffraction physics at hadron colliders, and (iii)
photon-photon collisions at very high energies: electroweak and beyond the
Standard Model processes. These mini-proceedings consist of an introduction and
short summaries of the talks presented at the meeting
Invariant higher-order variational problems II
Motivated by applications in computational anatomy, we consider a
second-order problem in the calculus of variations on object manifolds that are
acted upon by Lie groups of smooth invertible transformations. This problem
leads to solution curves known as Riemannian cubics on object manifolds that
are endowed with normal metrics. The prime examples of such object manifolds
are the symmetric spaces. We characterize the class of cubics on object
manifolds that can be lifted horizontally to cubics on the group of
transformations. Conversely, we show that certain types of non-horizontal
geodesics on the group of transformations project to cubics. Finally, we apply
second-order Lagrange--Poincar\'e reduction to the problem of Riemannian cubics
on the group of transformations. This leads to a reduced form of the equations
that reveals the obstruction for the projection of a cubic on a transformation
group to again be a cubic on its object manifold.Comment: 40 pages, 1 figure. First version -- comments welcome
Pastagem de Tifton 85 consorciado com forrageiras de inverno.
Experimento e AvaliaçÔes em Unidades de Produção; Manejo da Pastagem e MĂ©todo de Semeadura de Forrageiras de Inverno; Ăpoca e Densidade de Semeadura; Produção da Pastagem Consorciada; EspĂ©cies de Inverno para o ConsĂłrcio.bitstream/item/54182/1/CO-79.pd
Renormalization Group Flow in Scalar-Tensor Theories. II
We study the UV behaviour of actions including integer powers of scalar
curvature and even powers of scalar fields with Functional Renormalization
Group techniques. We find UV fixed points where the gravitational couplings
have non-trivial values while the matter ones are Gaussian. We prove several
properties of the linearized flow at such a fixed point in arbitrary dimensions
in the one-loop approximation and find recursive relations among the critical
exponents. We illustrate these results in explicit calculations in for
actions including up to four powers of scalar curvature and two powers of the
scalar field. In this setting we notice that the same recursive properties
among the critical exponents, which were proven at one-loop order, still hold,
in such a way that the UV critical surface is found to be five dimensional. We
then search for the same type of fixed point in a scalar theory with minimal
coupling to gravity in including up to eight powers of scalar curvature.
Assuming that the recursive properties of the critical exponents still hold,
one would conclude that the UV critical surface of these theories is five
dimensional.Comment: 14 pages. v.2: Minor changes, some references adde
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