5,868 research outputs found
BRST Analysis of Physical Fields and States for 4D Quantum Gravity on R x S^3
We consider the background-free quantum gravity based on conformal gravity
with the Riegert-Wess-Zumino action, which is formulated in terms of a
conformal field theory. Employing the background in practice, we
construct the nilpotent BRST operator imposing diffeomorphism invariance.
Physical fields and states are analyzed, which are given only by real primary
scalars with a definite conformal weight. With attention to the presence of
background charges, various significant properties, such as the state-operator
correspondence and the norm structure, are clarified with some examples.Comment: 29 pages, several descriptions written using CFT terminology are
adde
BRST Invariant Higher Derivative Operators in 4D Quantum Gravity based on CFT
We continue the study of physical fields for the background free 4D quantum
gravity based on the Riegert-Wess-Zumino action, developed in Phys. Rev. D {\bf
85} (2012) 024028. The background free model is formulated in terms of a
certain conformal field theory on M^4 in which conformal symmetry arises as
gauge symmetry, namely diffeomorphism invariance. In this paper, we construct
the physical field operator corresponding to any integer power of Ricci scalar
curvature in the context of the BRST quantization. We also discuss how to
define the correlation function and its physical meanings.Comment: 22 pages, minor typo corrected, published versio
Vertex Operators in 4D Quantum Gravity Formulated as CFT
We study vertex operators in 4D conformal field theory derived from quantized
gravity, whose dynamics is governed by the Wess-Zumino action by Riegert and
the Weyl action. Conformal symmetry is equal to diffeomorphism symmetry in the
ultraviolet limit, which mixes positive-metric and negative-metric modes of the
gravitational field and thus these modes cannot be treated separately in
physical operators. In this paper, we construct gravitational vertex operators
such as the Ricci scalar, defined as space-time volume integrals of them are
invariant under conformal transformations. Short distance singularities of
these operator products are computed and it is shown that their coefficients
have physically correct sign. Furthermore, we show that conformal algebra holds
even in the system perturbed by the cosmological constant vertex operator as in
the case of the Liouville theory shown by Curtright and Thorn.Comment: 26 pages, rewrote review part concisely, added explanation
Teleportation and entanglement distillation in the presence of correlation among bipartite mixed states
The teleportation channel associated with an arbitrary bipartite state
denotes the map that represents the change suffered by a teleported state when
the bipartite state is used instead of the ideal maximally entangled state for
teleportation. This work presents and proves an explicit expression of the
teleportation channel for the teleportation using Weyl's projective unitary
representation of the space of 2n-tuples of numbers from Z/dZ for integers d>1,
n>0, which has been known for n=1. This formula allows any correlation among
the n bipartite mixed states, and an application shows the existence of
reliable schemes for distillation of entanglement from a sequence of mixed
states with correlation.Comment: 12 pages, 1 figur
Making a Universe
For understanding the origin of anisotropies in the cosmic microwave
background, rules to construct a quantized universe is proposed based on the
dynamical triangulation method of the simplicial quantum gravity. A
-dimensional universe having the topology is created numerically in
terms of a simplicial manifold with -simplices as the building blocks. The
space coordinates of a universe are identified on the boundary surface , and the time coordinate is defined along the direction perpendicular
to . Numerical simulations are made mainly for 2-dimensional
universes, and analyzed to examine appropriateness of the construction rules by
comparing to analytic results of the matrix model and the Liouville theory.
Furthermore, a simulation in 4-dimension is made, and the result suggests an
ability to analyze the observations on anisotropies by comparing to the scalar
curvature correlation of a -surface formed as the last scattering
surface in the universe.Comment: 27pages,18figures,using jpsj.st
Practical Evaluation of Security for Quantum Key Distribution
Many papers proved the security of quantum key distribution (QKD) system, in
the asymptotic framework. The degree of the security has not been discussed in
the finite coding-length framework, sufficiently. However, to guarantee any
implemented QKD system requires, it is needed to evaluate a protocol with a
finite coding-length. For this purpose, we derive a tight upper bound of the
eavesdropper's information. This bound is better than existing bounds. We also
obtain the exponential rate of the eavesdropper's information. Further, we
approximate our bound by using the normal distribution.Comment: The manuscript has been modfie
Cost optimal energy retrofit strategies for public administrative buildings: A Cairo case study
The Egyptian government is currently constructing a new governmental quarter in the New Administrative Capital City, located east of Cairo. A planned relocation for all ministerial authorities to the New Capital City will leave a vacant governmental estate in Cairo. The study of the energy retrofit options provides a unique opportunity to reduce energy use and maximize the benefit from the anticipated investment in the re-use to be implemented within this stock. However, energy retrofit was found to be under-researched in the Egyptian context. This paper presents a pilot study that aims to identify cost optimal retrofit strategies for one of the soon to be vacated buildings, the Central Agency for Public Mobilization and Statistics (CAPMAS). Using DesignBuilder, an energy modelling study was implemented to estimate the existing performance of the building, assess the projected performance after a change of use (to an office building), and evaluate the cost optimality and the savings associated with the application of retrofit measures. The study found that the feasibility of implementing retrofit can be significantly offset by the discount rates in Egypt. As such, maintaining economic stability and considering non-economic incentives can be key drivers to increasing the energy retrofit uptake in Egypt
RNA secondary structure prediction from multi-aligned sequences
It has been well accepted that the RNA secondary structures of most
functional non-coding RNAs (ncRNAs) are closely related to their functions and
are conserved during evolution. Hence, prediction of conserved secondary
structures from evolutionarily related sequences is one important task in RNA
bioinformatics; the methods are useful not only to further functional analyses
of ncRNAs but also to improve the accuracy of secondary structure predictions
and to find novel functional RNAs from the genome. In this review, I focus on
common secondary structure prediction from a given aligned RNA sequence, in
which one secondary structure whose length is equal to that of the input
alignment is predicted. I systematically review and classify existing tools and
algorithms for the problem, by utilizing the information employed in the tools
and by adopting a unified viewpoint based on maximum expected gain (MEG)
estimators. I believe that this classification will allow a deeper
understanding of each tool and provide users with useful information for
selecting tools for common secondary structure predictions.Comment: A preprint of an invited review manuscript that will be published in
a chapter of the book `Methods in Molecular Biology'. Note that this version
of the manuscript may differ from the published versio
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