28,703 research outputs found
Effectiveness of tax incentives to boost (retirement) saving:theoretical motivation and empirical evidence
The adequacy of household saving for retirement has become a policy issue all around the world. The UK andUS have been in the vanguard of those countries that have tried to encourage retirement saving by providingtax-favoured treatment for particular savings accounts. We consider empirical evidence from these twocountries regarding the extent to which funds in some specific tax advantaged accounts (IRAs in the US,TESSAs and ISAs in the UK) represent new savings. Our best interpretation of this evidence is that: onlyrelatively small fractions of these funds can be considered to be ?new? saving and so these policies have been anexpensive means of encouraging saving; there has been some deadweight loss from the policies associated with?reshuffling? of existing savings. Continuing improvements in data on individual financial behaviour createscope for future empirical analysis of incentives to save, both within the standard economic framework that weexplain and exploit, and by considering extensions to and adaptations of it
String compactifications on Calabi-Yau stacks
In this paper we study string compactifications on Deligne-Mumford stacks.
The basic idea is that all such stacks have presentations to which one can
associate gauged sigma models, where the group gauged need be neither finite
nor effectively-acting. Such presentations are not unique, and lead to
physically distinct gauged sigma models; stacks classify universality classes
of gauged sigma models, not gauged sigma models themselves. We begin by
defining and justifying a notion of ``Calabi-Yau stack,'' recall how one
defines sigma models on (presentations of) stacks, and calculate of physical
properties of such sigma models, such as closed and open string spectra. We
describe how the boundary states in the open string B model on a Calabi-Yau
stack are counted by derived categories of coherent sheaves on the stack. Along
the way, we describe numerous tests that IR physics is
presentation-independent, justifying the claim that stacks classify
universality classes. String orbifolds are one special case of these
compactifications, a subject which has proven controversial in the past;
however we resolve the objections to this description of which we are aware. In
particular, we discuss the apparent mismatch between stack moduli and physical
moduli, and how that discrepancy is resolved.Comment: 85 pages, LaTeX; v2: typos fixe
Study on SPH Viscosity Term Formulations
For viscosity-dominated flows, the viscous effect plays a much more important role. Since the viscosity term in SPH-governing (Smoothed Particle Hydrodynamics) equations involves the discretization of a second-order derivative, its treatment could be much more challenging than that of a first-order derivative, such as the pressure gradient. The present paper summarizes a series of improved methods for modeling the second-order viscosity force term. By using a benchmark patch test, the numerical accuracy and efficiency of different approaches are evaluated under both uniform and non-uniform particle configurations. Then these viscosity force models are used to compute a documented lid-driven cavity flow and its interaction with a cylinder, from which the most recommended viscosity term formulation has been identified
High temperature phase of QCD
I give a brief overview of our present understanding of the high temperature
phase of QCD, trying to clarify some of the theoretical issues involved in the
current discussions that emphasize the strongly coupled character of the
quark-gluon plasma produced at RHIC.Comment: To appear in the proceedings of the International Conference on
Strong & Electroweak Matter, BNL, May 10-13 (2006), to be published in Nucl.
Phys. A 9 pages, 3 figures - late submission to the Archiv
Modeling Strategy for Injectivity in SWAG Processes
Imperial Users onl
Effectiveness of tax incentives to boost (retirement) saving: theoretical motivation and empirical evidence
The adequacy of household saving for retirement has become a policy issue all around the world. The UK and US have been in the vanguard of those countries that have tried to encourage retirement saving by providing tax-favoured treatment for particular savings accounts. We consider empirical evidence from these two countries regarding the extent to which funds in some specific tax advantaged accounts (IRAs in the US, TESSAs and ISAs in the UK) represent new savings. Our best interpretation of this evidence is that: only relatively small fractions of these funds can be considered to be "new" saving and so these policies have been an expensive means of encouraging saving; there has been some deadweight loss from the policies associated with "reshuffling" of existing savings. Continuing improvements in data on individual financial behaviour create scope for future empirical analysis of incentives to save, both within the standard economic framework that we explain and exploit, and by considering extensions to and adaptations of it.Saving, tax incentives to save, lifecycle model, household behaviour
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