118 research outputs found
Is Quantum Gravity a Chern-Simons Theory?
We propose a model of quantum gravity in arbitrary dimensions defined in
terms of the BV quantization of a supersymmetric, infinite dimensional matrix
model. This gives an (AKSZ-type) Chern-Simons theory with gauge algebra the
space of observables of a quantum mechanical Hilbert space H. The model is
motivated by previous attempts to formulate gravity in terms of
non-commutative, phase space, field theories as well as the Fefferman-Graham
curved analog of Dirac spaces for conformally invariant wave equations. The
field equations are flat connection conditions amounting to zero curvature and
parallel conditions on operators acting on H. This matrix-type model may give a
better defined setting for a quantum gravity path integral. We demonstrate that
its underlying physics is a summation over Hamiltonians labeled by a conformal
class of metrics and thus a sum over causal structures. This gives in turn a
model summing over fluctuating metrics plus a tower of additional modes-we
speculate that these could yield improved UV behavior.Comment: 22 pages, LaTeX, 3 figures, references added, version to appear in
PR
Quantum Gravity and Causal Structures: Second Quantization of Conformal Dirac Algebras
It is postulated that quantum gravity is a sum over causal structures coupled
to matter via scale evolution. Quantized causal structures can be described by
studying simple matrix models where matrices are replaced by an algebra of
quantum mechanical observables. In particular, previous studies constructed
quantum gravity models by quantizing the moduli of Laplace, weight and
defining-function operators on Fefferman-Graham ambient spaces. The algebra of
these operators underlies conformal geometries. We extend those results to
include fermions by taking an osp(1|2) "Dirac square root" of these algebras.
The theory is a simple, Grassmann, two-matrix model. Its quantum action is a
Chern-Simons theory whose differential is a first-quantized, quantum mechanical
BRST operator. The theory is a basic ingredient for building fundamental
theories of physical observables.Comment: 4 pages, LaTe
Gravity, Two Times, Tractors, Weyl Invariance and Six Dimensional Quantum Mechanics
Fefferman and Graham showed some time ago that four dimensional conformal
geometries could be analyzed in terms of six dimensional, ambient, Riemannian
geometries admitting a closed homothety. Recently it was shown how conformal
geometry provides a description of physics manifestly invariant under local
choices of unit systems. Strikingly, Einstein's equations are then equivalent
to the existence of a parallel scale tractor (a six component vector subject to
a certain first order covariant constancy condition at every point in four
dimensional spacetime). These results suggest a six dimensional description of
four dimensional physics, a viewpoint promulgated by the two times physics
program of Bars. The Fefferman--Graham construction relies on a triplet of
operators corresponding, respectively to a curved six dimensional light cone,
the dilation generator and the Laplacian. These form an sp(2) algebra which
Bars employs as a first class algebra of constraints in a six-dimensional gauge
theory. In this article four dimensional gravity is recast in terms of six
dimensional quantum mechanics by melding the two times and tractor approaches.
This "parent" formulation of gravity is built from an infinite set of six
dimensional fields. Successively integrating out these fields yields various
novel descriptions of gravity including a new four dimensional one built from a
scalar doublet, a tractor vector multiplet and a conformal class of metrics.Comment: 27 pages, LaTe
U(N|M) quantum mechanics on Kaehler manifolds
We study the extended supersymmetric quantum mechanics, with supercharges
transforming in the fundamental representation of U(N|M), as realized in
certain one-dimensional nonlinear sigma models with Kaehler manifolds as target
space. We discuss the symmetry algebra characterizing these models and, using
operatorial methods, compute the heat kernel in the limit of short propagation
time. These models are relevant for studying the quantum properties of a
certain class of higher spin field equations in first quantization.Comment: 21 pages, a reference adde
Inhibition of Sphingolipid Synthesis as a Phenotype-Modifying Therapy in Cystic Fibrosis
Cystic Fibrosis (CF) is an inherited disease associated with a variety of mutations affecting the CFTR gene. A deletion of phenylalanine 508 (F508) affects more than 70% of patients and results in unfolded proteins accumulation, originating a proteinopathy responsible for inflammation, impaired trafficking, altered metabolism, cholesterol and lipids accumulation, impaired autophagy at the cellular level. Lung inflammation has been extensively related to the accumulation of the lipotoxin ceramide. We recently proved that inhibition of ceramide synthesis by Myriocin reduces inflammation and ameliorates the defence response against pathogens infection, which is downregulated in CF. Here, we aim at demonstrating the mechanisms of Myriocin therapeutic effects in Cystic Fibrosis broncho-epithelial cells
Worldline approach to noncommutative field theory
The study of the heat-trace expansion in noncommutative field theory has
shown the existence of Moyal nonlocal Seeley-DeWitt coefficients which are
related to the UV/IR mixing and manifest, in some cases, the
non-renormalizability of the theory. We show that these models can be studied
in a worldline approach implemented in phase space and arrive to a master
formula for the -point contribution to the heat-trace expansion. This
formulation could be useful in understanding some open problems in this area,
as the heat-trace expansion for the noncommutative torus or the introduction of
renormalizing terms in the action, as well as for generalizations to other
nonlocal operators.Comment: 19 pages, version
Sphingolipid synthesis inhibition by myriocin administration enhances lipid consumption and ameliorates lipid response to myocardial ischemia reperfusion injury
Myocardial infarct requires prompt thrombolytic therapy or primary percutaneous coronary intervention to limit the extent of necrosis, but reperfusion creates additional damage. Along with reperfusion, a maladaptive remodeling phase might occur and it is often associated with inflammation, oxidative stress, as well as a reduced ability to recover metabolism homeostasis. Infarcted individuals can exhibit reduced lipid turnover and their accumulation in cardiomyocytes, which is linked to a deregulation of peroxisome proliferator activated receptors (PPARs), controlling fatty acids metabolism, energy production, and the anti-inflammatory response. We previously demonstrated that Myriocin can be effectively used as post-conditioning therapeutic to limit ischemia/reperfusion-induced inflammation, oxidative stress, and infarct size, in a murine model. In this follow-up study, we demonstrate that Myriocin has a critical regulatory role in cardiac remodeling and energy production, by up-regulating the transcriptional factor EB, PPARs nuclear receptors and genes involved in fatty acids metabolism, such as VLDL receptor, Fatp1, CD36, Fabp3, Cpts, and mitochondrial FA dehydrogenases. The overall effects are represented by an increased \u3b2-oxidation, together with an improved electron transport chain and energy production. The potent immunomodulatory and metabolism regulatory effects of Myriocin elicit the molecule as a promising pharmacological tool for post-conditioning therapy of myocardial ischemia/reperfusion injury
Quantum theories of (p,q)-forms
We describe quantum theories for massless (p,q)-forms living on Kaehler
spaces. In particular we consider four different types of quantum theories: two
types involve gauge symmetries and two types are simpler theories without gauge
invariances. The latter can be seen as building blocks of the former. Their
equations of motion can be obtained in a natural way by first-quantizing a
spinning particle with a U(2)-extended supersymmetry on the worldline. The
particle system contains four supersymmetric charges, represented quantum
mechanically by the Dolbeault operators and their hermitian conjugates. After
studying how the (p,q)-form field theories emerge from the particle system, we
investigate their one loop effective actions, identify corresponding heat
kernel coefficients, and derive exact duality relations. The dualities are seen
to include mismatches related to topological indices and analytic torsions,
which are computed as Tr(-1)^F and Tr[(-1)^F F] in the first quantized
supersymmetric nonlinear sigma model for a suitable fermion number operator F.Comment: 44 pages, 2 figures, a reference adde
Niveles de apoproteina-B y LDL- colesterol en una población joven de la ciudad de maracaibo
El presente estudio se propuso determinar si las concentraciones de apoproteína-B (g/L) se correlacionan con el LDL-colesterol (mg/dL) y al mismo tiempo, investigar la posibilidad de aplicarlas a la población de Maracaibo, en substitución de la fórmula de Friedewald de LDL-Colesterol. Las concentraciones séricas de la apoproteína-B fueron estudiadas en una muestra de 41 sujetos (27 hombres y 14 mujeres) con edades entre 20 y 39 años, usuarios del Laboratorio Clínico de la Escuela de Bioánalisis de La Universidad del Zulia, de la ciudad de Maracaibo. Se realizaron mediciones de glicemia, colesterol total, triacilglicéridos y el cálculo de LDL-C. La apoproteína-B fue determinada por un método inmunoturbidimétrico. Los valores de apoproteína-B ± DS fueron de 0.93 ± 0.3 g/L en el sexo femenino y de 1.06 ± 0.31 g/L en el sexo masculino. La correlación entre la apoproteína-B y el LDL-C fue de 0.8640. Al aplicar el análisis de regresión linear se obtuvieron fórmulas para el cálculo del LCL-C a partir de la concentración de apoproteína-B, representando un cálculo estadístico que deberá ser corroborado de manera experimental. El valor de riesgo de apoproteína -B
³ 1.2 g/L se ubicó en los percentiles 95 th para para el sexo femenino y 75 th para el masculino.
El presente estudio se propuso determinar si las concentraciones de apoproteína-B (g/L) se correlacionan con el LDL-colesterol (mg/dL) y al mismo tiempo, investigar la posibilidad de aplicarlas a la población de Maracaibo, en substitución de la fórmula de Friedewald de LDL-Colesterol. Las concentraciones séricas de la apoproteína-B fueron estudiadas en una muestra de 41 sujetos (27 hombres y 14 mujeres) con edades entre 20 y 39 años, usuarios del Laboratorio Clínico de la Escuela de Bioánalisis de La Universidad del Zulia, de la ciudad de Maracaibo. Se realizaron mediciones de glicemia, colesterol total, triacilglicéridos y el cálculo de LDL-C. La apoproteína-B fue determinada por un método inmunoturbidimétrico. Los valores de apoproteína-B ± DS fueron de 0.93 ± 0.3 g/L en el sexo femenino y de 1.06 ± 0.31 g/L en el sexo masculino. La correlación entre la apoproteína-B y el LDL-C fue de 0.8640. Al aplicar el análisis de regresión linear se obtuvieron fórmulas para el cálculo del LCL-C a partir de la concentración de apoproteína-B, representando un cálculo estadístico que deberá ser corroborado de manera experimental. El valor de riesgo de apoproteína -B ≥1.2 g/L se ubicó en los percentiles 95 th para para el sexo femenino y 75 th para el masculino.The purpose of this study was determine if the apolipoprotein-B concentrations (g/L) are correlated with the LDL-Cholesterol (mg/dL), and at the same time, to inquest the possibility to apply them to the population of Maracaibo, in substitution of the Friedewald formula for LDL-Cholesterol. The apolipoprotein-B serum concentrations were studied in a sample of 41 subjects (27 females and 14 males) between 20 and 39 years of age, users of the Bioanalisis School’s Clinical Laboratory, Zulia University in Maracaibo. Measurements of glycaemia, Total Cholesterol, Triglycerides and LDL-Cholesterol were made. The Apolipoprotein-B was determined by Inmunoturbidimetric method. The apolipoprotein-B levels were 0.93 ± 0.3 g/L in the female group and 1.06 ± 0.31 g/L in the male group. The correlation between apolipoprotein-B and LDLCholesterol was 0.8640. Linear regression analysis was applied, and formulas were obtained to calculate LDL-Cholesterol from apolipoprotein-B concentrations, representing a statistical formula that should be corroborated experimentally. The risk level of apolipoprotein-B (
³ 1.2 g/L) was set in the percentiles 95 th for females and 75 th for males.
 
Local Unit Invariance, Back-Reacting Tractors and the Cosmological Constant Problem
When physics is expressed in a way that is independent of local choices of
unit systems, Riemannian geometry is replaced by conformal geometry. Moreover
masses become geometric, appearing as Weyl weights of tractors (conformal
multiplets of fields necessary to keep local unit invariance manifest). The
relationship between these weights and masses is through the scalar curvature.
As a consequence mass terms are spacetime dependent for off-shell gravitational
backgrounds, but happily constant for physical, Einstein manifolds.
Unfortunately this introduces a naturalness problem because the scalar
curvature is proportional to the cosmological constant. By writing down tractor
stress tensors (multiplets built from the standard stress tensor and its first
and second derivatives), we show how back-reaction solves this naturalness
problem. We also show that classical back-reaction generates an interesting
potential for scalar fields. We speculate that a proper description of how
physical systems couple to scale, could improve our understanding of
naturalness problems caused by the disparity between the particle physics and
observed, cosmological constants. We further give some ideas how an ambient
description of tractor calculus could lead to a Ricci-flat/CFT correspondence
which generalizes the AdS side of Maldacena's duality to a Ricci-flat space of
one higher dimension.Comment: 20 pages, 2 figure
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