9,824 research outputs found
Topological Vertex, String Amplitudes and Spectral Functions of Hyperbolic Geometry
We discuss the homological aspects of the connection between quantum string
generating function and the formal power series associated to the dimensions of
chains and homologies of suitable Lie algebras. Our analysis can be considered
as a new straightforward application of the machinery of modular forms and
spectral functions (with values in the congruence subgroup of ) to the partition functions of Lagrangian branes, refined vertex and open
string partition functions, represented by means of formal power series that
encode Lie algebra properties. The common feature in our examples lies in the
modular properties of the characters of certain representations of the
pertinent affine Lie algebras and in the role of Selberg-type spectral
functions of an hyperbolic three-geometry associated with -series in the
computation of the string amplitudes.Comment: Revised version. References added, results remain unchanged. arXiv
admin note: text overlap with arXiv:hep-th/0701156, arXiv:1105.4571,
arXiv:1206.0664 by other author
High-Energy Proton-Proton Forward Scattering and Derivative Analyticity Relations
We present the results of several parametrizations to two different ensemble
of data on total cross sections at the highest
center-of-mass energies (including cosmic-ray information). The results are
statistically consistent with two distinct scenarios at high energies. From one
ensemble the prediction for the LHC ( TeV) is mb and from the other, mb. From each
parametrization, and making use of derivative analyticity relations (DAR), we
determine (ratio between the forward real and imaginary parts of the
elastic scattering amplitude). A discussion on the optimization of the DAR in
terms of a free parameter is also presented.In all cases good descriptions of
the experimental data are obtained.Comment: One formula added, one unit changed, small misprints corrected, final
version to be published in Brazilian Journal of Physics; 13 pages, 8 figures,
aps-revte
A conjecture on the infrared structure of the vacuum Schrodinger wave functional of QCD
The Schrodinger wave functional for the d=3+1 SU(N) vacuum is a partition
function constructed in d=4; the exponent 2S in the square of the wave
functional plays the role of a d=3 Euclidean action. We start from a
gauge-invariant conjecture for the infrared-dominant part of S, based on
dynamical generation of a gluon mass M in d=4. We argue that the exact leading
term, of O(M), in an expansion of S in inverse powers of M is a d=3
gauge-invariant mass term (gauged non-linear sigma model); the next leading
term, of O(1/M), is a conventional Yang-Mills action. The d=3 action that is
the sum of these two terms has center vortices as classical solutions. The d=3
gluon mass, which we constrain to be the same as M, and d=3 coupling are
related through the conjecture to the d=4 coupling strength, but at the same
time the dimensionless ratio in d=3 of mass to coupling squared can be
estimated from d=3 dynamics. This allows us to estimate the QCD coupling
in terms of this strictly d=3 ratio; we find a value of about
0.4, in good agreement with an earlier theoretical value but a little low
compared to QCD phenomenology. The wave functional for d=2+1 QCD has an
exponent that is a d=2 infrared-effective action having both the
gauge-invariant mass term and the field strength squared term, and so differs
from the conventional QCD action in two dimensions, which has no mass term.
This conventional d=2 QCD would lead in d=3 to confinement of all color-group
representations. But with the mass term (again leading to center vortices),
N-ality = 0 mod N representations are not confined.Comment: 15 pages, no figures, revtex
Dinâmica do carbono na regeneração natural em uma floresta manejada na Amazônia: estudo de caso Mil Madeiras Preciosas.
O futuro da Floresta Amazônica e as consequências que o desmatamento pode causar a mudança climática têm sido cada vez mais discutidos pela sociedade. Dessa forma, conhecer as consequências que as operações florestais irão trazer para a dinâmica das florestas manejadas é de extrema importância, mas precisamente nos termos da floresta está agindo como fonte ou sumidouro de carbono. Por esse motivo é importante estudar o ciclo do carbono na regeneração natural, já que a maior parte dos estudos de biomassa e carbono em florestas nativas se concentra na avaliação do estrato superior. Este trabalho utilizou dados de inventários florestais contínuos realizados na Fazenda Dois Mil, pertencente à empresa Mil Madeiras Preciosas, localizada no município de Itacoatiara-AM. O objetivo deste trabalho foi quantificar o estoque de carbono presente na regeneração natural de uma floresta manejada, assim como estudar a dinâmica do carbono e avaliar em diferentes períodos de monitoramento como a regeneração está se comportando após a exploração florestal.Dissertação (Mestrado em Ciências Florestais e Ambientais) - Universidade Federal do Amazonas, Manaus. Orientador: Dr. Celso Paulo de Azevedo; coorientadora: Dra. Cintia Rodrigues de Souza
Periodic Chaotic Billiards: Quantum-Classical Correspondence in Energy Space
We investigate the properties of eigenstates and local density of states
(LDOS) for a periodic 2D rippled billiard, focusing on their quantum-classical
correspondence in energy representation. To construct the classical
counterparts of LDOS and the structure of eigenstates (SES), the effects of the
boundary are first incorporated (via a canonical transformation) into an
effective potential, rendering the one-particle motion in the 2D rippled
billiard equivalent to that of two-interacting particles in 1D geometry. We
show that classical counterparts of SES and LDOS in the case of strong chaotic
motion reveal quite a good correspondence with the quantum quantities. We also
show that the main features of the SES and LDOS can be explained in terms of
the underlying classical dynamics, in particular of certain periodic orbits. On
the other hand, statistical properties of eigenstates and LDOS turn out to be
different from those prescribed by random matrix theory. We discuss the quantum
effects responsible for the non-ergodic character of the eigenstates and
individual LDOS that seem to be generic for this type of billiards with a large
number of transverse channels.Comment: 13 pages, 18 figure
Classical versus Quantum Structure of the Scattering Probability Matrix. Chaotic wave-guides
The purely classical counterpart of the Scattering Probability Matrix (SPM)
of the quantum scattering matrix is defined for 2D
quantum waveguides for an arbitrary number of propagating modes . We compare
the quantum and classical structures of for a waveguide
with generic Hamiltonian chaos. It is shown that even for a moderate number of
channels, knowledge of the classical structure of the SPM allows us to predict
the global structure of the quantum one and, hence, understand important
quantum transport properties of waveguides in terms of purely classical
dynamics. It is also shown that the SPM, being an intensity measure, can give
additional dynamical information to that obtained by the Poincar\`{e} maps.Comment: 9 pages, 9 figure
Population stability: regulating size in the presence of an adversary
We introduce a new coordination problem in distributed computing that we call
the population stability problem. A system of agents each with limited memory
and communication, as well as the ability to replicate and self-destruct, is
subjected to attacks by a worst-case adversary that can at a bounded rate (1)
delete agents chosen arbitrarily and (2) insert additional agents with
arbitrary initial state into the system. The goal is perpetually to maintain a
population whose size is within a constant factor of the target size . The
problem is inspired by the ability of complex biological systems composed of a
multitude of memory-limited individual cells to maintain a stable population
size in an adverse environment. Such biological mechanisms allow organisms to
heal after trauma or to recover from excessive cell proliferation caused by
inflammation, disease, or normal development.
We present a population stability protocol in a communication model that is a
synchronous variant of the population model of Angluin et al. In each round,
pairs of agents selected at random meet and exchange messages, where at least a
constant fraction of agents is matched in each round. Our protocol uses
three-bit messages and states per agent. We emphasize that
our protocol can handle an adversary that can both insert and delete agents, a
setting in which existing approximate counting techniques do not seem to apply.
The protocol relies on a novel coloring strategy in which the population size
is encoded in the variance of the distribution of colors. Individual agents can
locally obtain a weak estimate of the population size by sampling from the
distribution, and make individual decisions that robustly maintain a stable
global population size
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