4,801 research outputs found
Conformal anomaly from gauge fields without gauge fixing
We show how the Weyl anomaly generated by gauge fields, can be computed from
manifestly gauge invariant and diffeomorphism invariant exact renormalization
group equations, without having to fix the gauge at any stage. Regularisation
is provided by covariant higher derivatives and by embedding the Maxwell field
into a spontaneously broken supergauge theory. We first provide a
realisation that leaves behind two versions of the original gauge field,
and then construct a manifestly supergauge invariant flow equation
which leaves behind only the original Maxwell field in the spontaneously broken
regime.Comment: 24 page
The hardwiring of development: Organization and function of genomic regulatory systems
The gene regulatory apparatus that directs development is
encoded in the DNA, in the form of organized arrays of
transcription factor target sites. Genes are regulated by
interactions with multiple transcription factors and the
target sites for the transcription factors required for the
control of each gene constitute its cis-regulatory system.
These systems are remarkably complex. Their hardwired
internal organization enables them to behave as genomic
information processing systems. Developmental gene regulatory
networks consist of the cis-regulatory systems of all
the relevant genes and the regulatory linkages amongst
them. Though there is yet little explicit information, some
general properties of genomic regulatory networks have
become apparent. The key to understanding how genomic
regulatory networks are organized, and how they work, lies
in experimental analysis of cis-regulatory systems at all
levels of the regulatory network
Macroeconomic Effects of Deregulation in Goods Market with Heterogeneous Firms
This paper builds on the Blanchard and Giavazzi (2003) model of deregulation. We concentrate on product market to construct a framework explaining in a more nuanced way the redistributive effects of deregulation between sectors and within the same sector, and possible oppositions to this policy by firms and workers. In a general equilibrium framework, we introduce two sectors(regulated and unregulated), heterogeneity in firms' productivity, and aā¦fixed cost of entry. In such a context effects of deregulation policies can be ambiguous depending on some parametric restrictions, and sometime counterproductive. As a result, deregulation policies are not always welfare improving: a deregulation action will succeed in increasing competition and reducing mark up when the economy is already partially deregulated (sufficiently high level of competition), but may achieve the opposite outcome when it is highly regulated. Additionally, we study the choice of the best policy instrument and the optimal sequencing in the use of instruments.
Exact renormalization group equation in presence of rescaling anomaly
Wilson's approach to renormalization group is reanalyzed for supersymmetric
Yang-Mills theory. Usual demonstration of exact renormalization group equation
must be modified due to the presence of the so called Konishi anomaly under the
rescaling of superfields. We carry out the explicit computation for N=1 SUSY
Yang-Mills theory with the simpler, gauge invariant regularization method,
recently proposed by Arkani-Hamed and Murayama. The result is that the
Wilsonian action S_M consists of two terms, i.e. the non anomalous term, which
obeys Polchinski's flow equation and Fujikawa-Konishi determinant contribution.
This latter is responsible for Shifman-Vainshtein relation of exact
beta-function.Comment: 19 pages, no figures; an appendix and reference added; typos
correcte
Navier-Stokes turbine heat transfer predictions using two-equation turbulence
Navier-Stokes calculations were carried out in order to predict the heat transfer rates on turbine blades. The calculations were performed using TRAF2D which is a two-dimensional, explicit, finite volume mass-averaged Navier-Stokes solver. Turbulence was modeled using q-omega and k-epsilon two-equation models and the Baldwin-Lomax algebraic model. The model equations along with the flow equations were solved explicitly on a non-periodic C grid. Implicit residual smoothing (IRS) or a combination of multigrid technique and IRS was applied to enhance convergence rates. Calculations were performed to predict the Stanton number distributions on the first stage vane and blade row as well as the second stage vane row of the Rocketdyne Space Shuttle Main Engine (SSME) high pressure fuel turbine. The comparison with the experimental results, although generally favorable, serves to highlight the weaknesses of the turbulence models and the possible areas of improving these models for use in turbomachinery heat transfer calculations
External debt sustainability and domestic debt in Heavily Indebted Poor Countries
In this paper we stress the limits of the current debt sustainability framework used in the IMF-WB HIPC Initiative and the necessity to include domestic public debt into the analysis. The standard sustainability analysis does not take into account the fully-fledged budget constraint and the feedback effects of the fiscal and monetary adjustment required by multilateral programs. The switch from foreign to domestic borrowing, and rising domestic real interest rates are likely to undermine the overall sustainability and the success of debt relief programs. This work focuses on the evaluation of public debt sustainability in a simple accounting framework. We use data on external public debt (multilateral and bilateral) and on domestic public debt to underline how the inclusion of domestic debt into the analysis undermines the sustainability target.HIPC; Domestic debt; Debt sustainability; Debt Relief
N=1* model superpotential revisited (IR behaviour of N=4 limit)
The one-loop contribution to the superpotential, in particular the
Veneziano-Yankielowicz potential in N=1 supersymmetric Yang-Mills model is
discussed from an elementary field theory method and the matrix model point of
view. Both approaches are based on the Renormalization Group variation of the
superconformal N=4 supersymmetric Yang-Mills model.Comment: 31 page
Universality From Very General Nonperturbative Flow Equations in QCD
In the context of very general exact renormalization groups, it will be shown
that, given a vertex expansion of the Wilsonian effective action, remarkable
progress can be made without making any approximations. Working in QCD we will
derive, in a manifestly gauge invariant way, an exact diagrammatic expression
for the expectation value of an arbitrary gauge invariant operator, in which
many of the non-universal details of the setup do not explicitly appear. This
provides a new starting point for attacking nonperturbative problems.Comment: 4 pages, 1 figur
Donor/Acceptor Heterojunction Organic Solar Cells
The operation and the design of organic solar cells with donor/acceptor heterojunction structure and exciton blocking layer is outlined and results of their initial development and assessment are reported. Under halogen lamp illumination with 100 mW/cm2 incident optical power density, the devices exhibits an open circuit voltage VOC = 0.45 V, a short circuit current density JSC between 2 and 2.5 mA/cm2 with a fill factor FF ā 50%, an external quantum efficiency (electrons/s over incident photons/s) EQE ā 5% and a power conversion efficiency of about 0.5%. Measurements of the photoelectrical characteristics with time are also reported, confirming that non encapsulated organic solar cells have limited stability in ambient atmosphere
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