13,230 research outputs found
General solution of an exact correlation function factorization in conformal field theory
We discuss a correlation function factorization, which relates a three-point
function to the square root of three two-point functions. This factorization is
known to hold for certain scaling operators at the two-dimensional percolation
point and in a few other cases. The correlation functions are evaluated in the
upper half-plane (or any conformally equivalent region) with operators at two
arbitrary points on the real axis, and a third arbitrary point on either the
real axis or in the interior. This type of result is of interest because it is
both exact and universal, relates higher-order correlation functions to
lower-order ones, and has a simple interpretation in terms of cluster or loop
probabilities in several statistical models. This motivated us to use the
techniques of conformal field theory to determine the general conditions for
its validity.
Here, we discover a correlation function which factorizes in this way for any
central charge c, generalizing previous results. In particular, the
factorization holds for either FK (Fortuin-Kasteleyn) or spin clusters in the
Q-state Potts models; it also applies to either the dense or dilute phases of
the O(n) loop models. Further, only one other non-trivial set of highest-weight
operators (in an irreducible Verma module) factorizes in this way. In this case
the operators have negative dimension (for c < 1) and do not seem to have a
physical realization.Comment: 7 pages, 1 figure, v2 minor revision
Energy storage-boiler tank
Activities performed in an effort to demonstrate heat of fusion energy storage in containerized salts are reported. The properties and cycle life characteristics of a eutectic salt having a boiling point of about 385 C (NaCl, KCl, Mg Cl2) were determined. M-terphenyl was chosen as the heat transfer fluid. Compatibility studies were conducted and mild steel containers were selected. The design and fabrication of a 2MWh storage boiler tank are discussed
Contextuality under weak assumptions
The presence of contextuality in quantum theory was first highlighted by Bell, Kochen and Specker, who discovered that for quantum systems of three or more dimensions, measurements could not be viewed as deterministically revealing pre-existing properties of the system. More precisely, no model can assign deterministic outcomes to the projectors of a quantum measurement in a way that depends only on the projector and not the context (the full set of projectors) in which it appeared, despite the fact that the Born rule probabilities associated with projectors are independent of the context. A more general, operational definition of contextuality introduced by Spekkens, which we will term "probabilistic contextuality", drops the assumption of determinism and allows for operations other than measurements to be considered contextual. Even two-dimensional quantum mechanics can be shown to be contextual under this generalised notion. Probabilistic noncontextuality represents the postulate that elements of an operational theory that cannot be distinguished from each other based on the statistics of arbitrarily many repeated experiments (they give rise to the same operational probabilities) are ontologically identical. In this paper, we introduce a framework that enables us to distinguish between different noncontextuality assumptions in terms of the relationships between the ontological representations of objects in the theory given a certain relation between their operational representations. This framework can be used to motivate and define a "possibilistic" analogue, encapsulating the idea that elements of an operational theory that cannot be unambiguously distinguished operationally can also not be unambiguously distinguished ontologically. We then prove that possibilistic noncontextuality is equivalent to an alternative notion of noncontextuality proposed by Hardy. Finally, we demonstrate that these weaker noncontextuality assumptions are sufficient to prove alternative versions of known "no-go" theorems that constrain ψ-epistemic models for quantum mechanics
Maximizing phonon thermal conductance for ballistic membranes
At low temperatures, phonon scattering can become so weak that phonon
transport becomes ballistic. We calculate the ballistic phonon conductance G
for membranes using elasticity theory, considering the transition from three to
two dimensions. We discuss the temperature and thickness dependence and
especially concentrate on the issue of material parameters. For all membrane
thicknesses, the best conductors have, counter-intuitively, the lowest speed of
sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc
Combinatorial Bounds and Characterizations of Splitting Authentication Codes
We present several generalizations of results for splitting authentication
codes by studying the aspect of multi-fold security. As the two primary
results, we prove a combinatorial lower bound on the number of encoding rules
and a combinatorial characterization of optimal splitting authentication codes
that are multi-fold secure against spoofing attacks. The characterization is
based on a new type of combinatorial designs, which we introduce and for which
basic necessary conditions are given regarding their existence.Comment: 13 pages; to appear in "Cryptography and Communications
The Location of the Nucleus of NGC 1068 and the Three-dimensional Structure of Its Nuclear Region
The HST archival UV imaging polarimetry data of NGC 1068 is re-examined.
Through an extensive estimation of the observational errors, we discuss whether
the distribution of the position angles (PAs) of polarization is simply
centrosymmetric or not. Taking into account the effect of a bad focus at the
time of the observation, we conclude that, within the accuracy of HST/FOC
polarimetry, the PA distribution is completely centrosymmetric. This means that
the UV polarization originates only from scattering of the radiation from a
central point-like source.
However, our analysis shows that the most probable location of the nucleus is
only ~0.''08 (~6pc) south from the brightest cloud called ``cloud B''. The
error circle of 99% confidence level extends to cloud B and to ``cloud A''
which is about 0.''2 south of cloud B. By this FOC observation, Cloud B is only
marginally rejected as the nucleus.
Assuming that the UV flux is dominated by electron-scattered light, we have
also derived a three-dimensional structure of the nuclear region. The inferred
distribution suggests a linear structure which could be related to the radio
jet.Comment: 19 pages, 14 figures, to be published in the Astrophysical Journa
The mission oriented terminal area simulation facility
The Mission Oriented Terminal Area Simulation (MOTAS) was developed to provide an ATC environment in which flight management and flight operations research studies can be conducted with a high degree of realism. This facility provides a flexible and comprehensive simulation of the airborne, ground-based and communication aspects of the airport terminal area environment. Major elements of the simulation are: an airport terminal area environment model, two air traffic controller stations, several aircraft models and simulator cockpits, four pseudo pilot stations, and a realistic air-ground communications network. MOTAS has been used for one study with the DC-9 simulator and a series of data link studies are planned in the near future
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