792 research outputs found
Nonperturbative renomalization group for Einstein gravity with matter
we investigate the exact renormalization group (RG) in Einstein gravity
coupled to N-component scalar field, working in the effective average action
formalism and background field method. The truncated evolution equation is
obtained for the Newtonian and cosmological constants. We have shown that
screening or antiscreening behaviour of the gravitational coupling depends
cricially on the choice of scalar-gravitational and the number of scalar
fields.Comment: 7 pages, LaTeX, a few typos correcte
Quantum properties of general gauge theories with composite and external fields
The generating functionals of Green's functions with composite and external
fields are considered in the framework of BV and BLT quantization methods for
general gauge theories. The corresponding Ward identities are derived and the
gauge dependence is investigatedComment: 24 pages, LATEX, slightly changed to clarify the essential new aspect
concerning composite fields depending on external ones; added formulas
showing lack of (generalized) nilpotence of operators appearing in the Ward
identitie
Evolving information systems: meeting the ever-changing environment
To meet the demands of organizations and their ever-changing environment, information systems are required which are able to evolve to the same extent as organizations do. Such a system has to support changes in all time-and application-dependent aspects. In this paper, requirements and a conceptual framework for evolving information systems are presented. This framework includes an architecture for such systems and a revision of the traditional notion of update. Based on this evolutionary notion of update (recording, correction and forgetting) a state transition-oriented model on three levels of abstraction (event level, recording level, correction level) is introduced. Examples are provided to illustrate the conceptual framework for evolving information systems
Gauge Consistent Wilson Renormalization Group I: Abelian Case
A version of the Wilson Renormalization Group Equation consistent with gauge
symmetry is presented. A perturbative renormalizability proof is established. A
wilsonian derivation of the Callan-Symanzik equation is given.Comment: Latex2e, 39 pages, 3 eps figures. Revised version to appear in Int.
J. Mod. Phy
Determination of quantitative and site-specific DNA methylation of perforin by pyrosequencing
<p>Abstract</p> <p>Background</p> <p>Differential expression of perforin (<it>PRF1</it>), a gene with a pivotal role in immune surveillance, can be attributed to differential methylation of CpG sites in its promoter region. A reproducible method for quantitative and CpG site-specific determination of perforin methylation is required for molecular epidemiologic studies of chronic diseases with immune dysfunction.</p> <p>Findings</p> <p>We developed a pyrosequencing based method to quantify site-specific methylation levels in 32 out of 34 CpG sites in the <it>PRF1 </it>promoter, and also compared methylation pattern in DNAs extracted from whole blood drawn into PAXgene blood DNA tubes (whole blood DNA) or DNA extracted from peripheral blood mononuclear cells (PBMC DNA) from the same normal subjects. Sodium bisulfite treatment of DNA and touchdown PCR were highly reproducible (coefficient of variation 1.63 to 2.18%) to preserve methylation information. Application of optimized pyrosequencing protocol to whole blood DNA revealed that methylation level varied along the promoter in normal subjects with extremely high methylation (mean 86%; range 82–92%) in the distal enhancer region (CpG sites 1–10), a variable methylation (range 49%–83%) in the methylation sensitive region (CpG sites 11–17), and a progressively declining methylation level (range 12%–80%) in the proximal promoter region (CpG sites 18–32) of <it>PRF1</it>. This pattern of methylation remained the same between whole blood and PBMC DNAs, but the absolute values of methylation in 30 out of 32 CpG sites differed significantly, with higher values for all CpG sites in the whole blood DNA.</p> <p>Conclusion</p> <p>This reproducible, site-specific and quantitative method for methylation determination of <it>PRF1 </it>based on pyrosequencing without cloning is well suited for large-scale molecular epidemiologic studies of diseases with immune dysfunction. PBMC DNA may be better suited than whole blood DNA for examining methylation levels in genes associated with immune function.</p
Is Quantum Einstein Gravity Nonperturbatively Renormalizable?
We find considerable evidence supporting the conjecture that four-dimensional
Quantum Einstein Gravity is ``asymptotically safe'' in Weinberg's sense. This
would mean that the theory is likely to be nonperturbatively renormalizable and
thus could be considered a fundamental (rather than merely effective) theory
which is mathematically consistent and predictive down to arbitrarily small
length scales. For a truncated version of the exact flow equation of the
effective average action we establish the existence of a non-Gaussian
renormalization group fixed point which is suitable for the construction of a
nonperturbative infinite cutoff-limit. The truncation ansatz includes the
Einstein-Hilbert action and a higher derivative term.Comment: 18 pages, latex, 3 figure
Effective Average Action in N=1 Super-Yang-Mills Theory
For N=1 Super-Yang-Mills theory we generalize the effective average action
Gamma_k in a manifest supersymmetric way using the superspace formalism. The
exact evolution equation for Gamma_k is derived and, introducing as an
application a simple truncation, the standard one-loop beta-function of N=1 SYM
theory is obtained.Comment: 17 pages, LaTeX, some remarks added, misprints corrected, to appear
in Phys. Rev.
Phase transitions in two dimensions - the case of Sn adsorbed on Ge(111) surfaces
Accurate atomic coordinates of the room-temperature (root3xroot3)R30degree
and low-temperature (3x3) phases of 1/3 ML Sn on Ge(111) have been established
by grazing-incidence x-ray diffraction with synchrotron radiation. The Sn atoms
are located solely at T4-sites in the (root3xroot3)R30degree structure. In the
low temperature phase one of the three Sn atoms per (3x3) unit cell is
displaced outwards by 0.26 +/- 0.04 A relative to the other two. This
displacement is accompanied by an increase in the first to second double-layer
spacing in the Ge substrate.Comment: RevTeX, 5 pages including 2 figure
Scalar-QED \beta-functions near Planck's Scale
The Renormalization Group Flow Equations of the Scalar-QED model near
Planck's scale are computed within the framework of the average effective
action. Exact Flow Equations, corrected by Einstein Gravity, for the running
self-interacting scalar coupling parameter and for the running v.e.v. of
, are computed taking into account threshold effects. Analytic
solutions are given in the infrared and ultraviolet limits.Comment: 19 pp, Latex; typos corrected and references added. To appear in the
Int. J. Mod. Phys.
Renormalization Group Flow of Quantum Gravity in the Einstein-Hilbert Truncation
The exact renormalization group equation for pure quantum gravity is used to
derive the non-perturbative \Fbeta-functions for the dimensionless Newton
constant and cosmological constant on the theory space spanned by the
Einstein-Hilbert truncation. The resulting coupled differential equations are
evaluated for a sharp cutoff function. The features of these flow equations are
compared to those found when using a smooth cutoff. The system of equations
with sharp cutoff is then solved numerically, deriving the complete
renormalization group flow of the Einstein-Hilbert truncation in . The
resulting renormalization group trajectories are classified and their physical
relevance is discussed. The non-trivial fixed point which, if present in the
exact theory, might render Quantum Einstein Gravity nonperturbatively
renormalizable is investigated for various spacetime dimensionalities.Comment: 58 pages, latex, 24 figure
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