3,059 research outputs found
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
Recursion Relations in Liouville Gravity coupled to Ising Model satisfying Fusion Rules
The recursion relations of 2D quantum gravity coupled to the Ising model
discussed by the author previously are reexamined. We study the case in which
the matter sector satisfies the fusion rules and only the primary operators
inside the Kac table contribute. The theory involves unregularized divergences
in some of correlators. We obtain the recursion relations which form a closed
set among well-defined correlators on sphere, but they do not have a beautiful
structure that the bosonized theory has and also give an inconsistent result
when they include an ill-defined correlator with the divergence. We solve them
and compute the several normalization independent ratios of the well-defined
correlators, which agree with the matrix model results.Comment: Latex, 22 page
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
Impact of Tributyltin and Triphenyltin on Ivory Shell (Babylonia japonica) Populations
We histopathologically examined gonads and chemically determined organotin compounds in tissues of the ivory shell, Babylonia japonica. Imposex (a superimposition of male-type genital organs on females) occurred in approximately 80–90% of B. japonica specimens that we examined, with the penis and vas deferens both well developed. No oviduct blockage by vas deferens formation was observed. Ovarian spermatogenesis and suppressed ovarian maturation were observed in the females that exhibited imposex, although no histopathological abnormalities were found in males. Tissue distributions of organotin compounds [tributyltin (TBT), triphenyltin (TPhT), and their metabolites] were different for butyltins and phenyltins; a remarkably high accumulation of TBT was observed in the ctenidium, osphradium, and heart, whereas high concentrations of TPhT were detected in the ovary and digestive gland. More than one-third of TBT accumulated in the digestive glands of both males and females, followed by the testis, ctenidium, muscle, and heart tissues in males and in the muscle, ovary, ctenidium, and head tissues (including the central nervous system ganglia) in females. In both males and females, more than half of total TPhT accumulated in the digestive glands, followed by the gonads. The next highest values were in the muscle, ctenidium, and heart tissues in males and in the muscle, oviduct, and head tissues in females. Both TBT and TPhT concentrations in the gonads were positively correlated with penis length in females. Our findings strongly suggest that reproductive failure in adult females accompanied by imposex, possibly induced by TBT and TPhT from antifouling paints, may have caused the marked decline of B. japonica populations in Japan
Data-Driven Analysis of Pareto Set Topology
When and why can evolutionary multi-objective optimization (EMO) algorithms
cover the entire Pareto set? That is a major concern for EMO researchers and
practitioners. A recent theoretical study revealed that (roughly speaking) if
the Pareto set forms a topological simplex (a curved line, a curved triangle, a
curved tetrahedron, etc.), then decomposition-based EMO algorithms can cover
the entire Pareto set. Usually, we cannot know the true Pareto set and have to
estimate its topology by using the population of EMO algorithms during or after
the runtime. This paper presents a data-driven approach to analyze the topology
of the Pareto set. We give a theory of how to recognize the topology of the
Pareto set from data and implement an algorithm to judge whether the true
Pareto set may form a topological simplex or not. Numerical experiments show
that the proposed method correctly recognizes the topology of high-dimensional
Pareto sets within reasonable population size.Comment: 8 pages, accepted at GECCO'18 as a full pape
Variación en parámetros bioquímicos en un grupo de pacientes con tumor cerebral primario: revisión de cuatro estudios
Introduction: It has been well established and evidence-based fact that serum levels of proteins, cholesterol, trace elements, andpseudouridines may suffer changes during a neoplastic disease process. This report encompassed four prospective studies, original in Iraq to our knowledge, had explored the serum total proteins (TP), pseudouridines levels, total serum cholesterol (TSC), and serum trace elements (TE), in groups of patients harboring primary brain tumours (PBT) compared to healthy persons. Patients and Methods:Study number 1: A group of 107 patients, from both sexes, aged 2-75 years, harboring PBT were admitted to and operated upon via formal craniotomy by staff neurosurgeons at The Teaching Hospital at Kadhimiyah (TTHK) and Neurosurgical Hospital (NH); their sera were tested for serum total proteins (TP); the latter biochemical parameters were compared with those of 40 healthy persons. Study number II: the same patients and healthy controls were tested for pseudouridine measurement. Study number III: Another group of 30 patients with PBT were studied for TSC levels and were compared with 30 healthy volunteers. Study number IV: A third group of 26 patients with PBT, from both sexes, their sera were tested and measured for TE; the measurements were compared to 1630 volunteers from both sexes and of different age groups. The sera and brain tumor tissue samples were analysed and examined by appropriate methods at relevant laboratories of the TTHK, NH, The Medical Research Centre (MRC) of The College of Medicine, Al-Nahrain University and the Iraqi Atomic Energy Committee (IAEC). Results and Discussion: The serum TP and PBT study: Results are shown in table 1. The serum pseudouridines and PBT study: Mean levels of pseudouridine in serum of PBT patients, were significantly higher (p < 0.01) than its levels in the (normal) controls, table 2. The TSC and PBT study: 1. Hesalthy persons from both sexes: age range, in years, 15 – 75, mean 40.5, SD ± 19.8; TSC range 142 – 230 mg / dl, mean 185.6 mg / dl, SD ± 24.9, (3.7 – 5.9 mmol / l, mean 4.8 mmol / l, SD± 0.6), table 3. 2. Thirty persons from both sexes having peripheral tumors, with no clinical evidence of brain tumors: age range, in years, 15 – 75, mean 54.3 ± 12.8; TSC range 90 – 220 mg / dl, 143 ± 36.3 (2.3 – 5.7 mmol / l, mean 3.7 ± 0.9), table 4. 3. Thirty patients from both sexes with primary and secondary brain tumors, age range, in years, 15 - 75, mean 41.3 ± 20.9; TSC range 140 – 284 mg / dl, 217.6 ± 41.2 (3.6 – 7.3 mmol / l, 5.6 ±1.1), table 4. Study number IV: Serum mean values (and S.D.) of all measured TEs were as follow: Se 0.045 +/- 0.011, Zn 0.320 +/- 0.095, Cu 0.607 +/- 0.154, Fe 0.880 +/- 0.456, Mg 13.625 +/- 3.994, Co 0.020 +/- 0.036, Ni 0.016 +/- 0.030, Mn 0.016 +/- 0.009, Cd 0.050 (one sample), and Cr 0.015 +/- 0.005 micrograms per milliliter (mcg / ml). All mean concentrations were consistently lower in the patients than healthy volunteers; both the Student’s (t) and probability (p value) tests were performed; for Se, Zn, Cu, Mg, Co, Ni, Mn, and Cr the p value was <0.01 showing statistically significant results; however, for Fe, though the mean concentration was also lower in the brain tumor group, there was no statistical significance, p > 0.05. Due to technical difficulties and very low concentration of Cd, it was not measured in healthy volunteers; however, it was measured in only one patient’s serum sample; this has been discarded from the study, table 5. Conclusions: Levels of serum TP, TC, and pseudouridine are higher in patients with PBT than in healthy people; however, those of serum TE are lower in the PBT group than healthy persons; the results of this report are in keeping with those of other researchers. The biochemical parameters can be an additional laboratory monitor in the investigation of PBT patients; however, both the specificity and sensitivity need to be ascertained. To our knowledge, this was the first study to be performed in Iraq in the setting of PB
Entanglement-assisted quantum low-density parity-check codes
This paper develops a general method for constructing entanglement-assisted
quantum low-density parity-check (LDPC) codes, which is based on combinatorial
design theory. Explicit constructions are given for entanglement-assisted
quantum error-correcting codes (EAQECCs) with many desirable properties. These
properties include the requirement of only one initial entanglement bit, high
error correction performance, high rates, and low decoding complexity. The
proposed method produces infinitely many new codes with a wide variety of
parameters and entanglement requirements. Our framework encompasses various
codes including the previously known entanglement-assisted quantum LDPC codes
having the best error correction performance and many new codes with better
block error rates in simulations over the depolarizing channel. We also
determine important parameters of several well-known classes of quantum and
classical LDPC codes for previously unsettled cases.Comment: 20 pages, 5 figures. Final version appearing in Physical Review
Pressure Effects in Manganites with Layered Perovskite Structure
Pressure effects on the charge and spin dynamics in the bilayer manganite
compounds are studied theoretically by taking into
account the orbital degrees of freedom. The orbital degrees are active in the
layered crystal structure, and applied hydrostatic pressure stabilizes the
orbital in comparison with . The change of the
orbital states weakens the interlayer charge and spin couplings, and suppresses
the three dimensional ferromagnetic transition. Numerical results, based on an
effective Hamiltonian which includes the energy level difference of the
orbitals, show that the applied pressure controls the dimensionality of the
spin and charge dynamics through changes of the orbital states.Comment: 5 pages, 2 figure
Size, Shape and Low Energy Electronic Structure of Carbon Nanotubes
A theory of the long wavelength low energy electronic structure of
graphite-derived nanotubules is presented. The propagating electrons are
described by wrapping a massless two dimensional Dirac Hamiltonian onto a
curved surface. The effects of the tubule size, shape and symmetry are included
through an effective vector potential which we derive for this model. The rich
gap structure for all straight single wall cylindrical tubes is obtained
analytically in this theory, and the effects of inhomogeneous shape
deformations on nominally metallic armchair tubes are analyzed.Comment: 5 pages, 3 postscript figure
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