6,007 research outputs found
Formation of Black Holes in Topologically Massive Gravity
We present an exact solution in 3-dimensional topologically massive gravity
with negative cosmological constant which dynamically interpolates between a
past horizon and a chiral AdS pp-wave. Similarly, upon time reversal, one
obtains an AdS pp-wave with a future event horizonComment: Improved presentation. Extended discussion of linear stability and
regularity of the metric. Added reference
On the Canonical Equivalence of Liouville and Free Fields
We obtain the parity invariant generating functional for the canonical
transformation mapping the Liouville theory into a free scalar field and
explain how it is related to the pseudoscalar transformationComment: 8 pages, Latex, Important earlier work by G.P. Jordadze acknowledge
Non-Abelian Born-Infeld Action and Solitons for Critical Non-BPS Branes
The non-abelian flat directions in the tachyon potential of stable non-BPS
branes recently found are shown to persist to all orders in alpha' at tree
level in the string coupling. We also obtain the non-abelian Born-Infeld action
including the tachyon potential for a stack of stable non-BPS branes on a
critical orbifold. Finally we discuss stable soliton states on the non-BPS
brane.Comment: 12+1 pages, Latex. Typos, a reference and the discussion of the
monopole solution are correcte
Brief Resume of Seiberg-Witten Theory
Talk presented by the second author at the Inaugural Coference of the Asia
Pacific Center for Theoretical Physics, Seoul, June 1996. The purpose of this
note is to give a resume of the Seiberg-Witten theory in the simplest possible
mathematical terms.Comment: 10 pages, LaTe
Fiscal Federalism and Optimum Currency Areas: Evidence for Europe From the United States
The main goal of this paper is to estimate to what extent the federal government of the United States insures member states against regional income shocks. We find that a one dollar reduction in a region's per capita personal income triggers a decrease in federal taxes of about 34 cents and an increase in federal transfers of about 6 cents. Hence, the final reduction in disposable per capita income is on the order of 60 cents. That is, between one third and one half of the initial shock is absorbed by the federal government. The much larger reaction of taxes than transfers to these regional imbalances reflects the fact that the main mechanism at work is the federal income tax system which in turn means that the stabilization process is automatic rather than specifically designed each time there is a cyclical movement in income. Some economists may want to argue that this regional insurance scheme provided by the federal government is an important reason why the system of fixed exchange rates that exists within the United States today has survived without major problems. Under this view, the creation of a European Central Bank that issues unified European currency without the simultaneous introduction (or expansion) of a fiscal federalist system could put the project at risk. Rough calculations of the impact of the existing European tax system on regional income suggests that a one dollar shock to regional GDP will reduce tax payments to the EEC government by half a cent!. Hence, the current European tax system has a long way to go before it reaches the 34 cents of the U.S. Federal Government.
Adhesion and electronic structure of graphene on hexagonal boron nitride substrates
We investigate the adsorption of graphene sheets on h-BN substrates by means
of first-principles calculations in the framework of adiabatic connection
fluctuation-dissipation theory in the random phase approximation. We obtain
adhesion energies for different crystallographic stacking configurations and
show that the interlayer bonding is due to long-range van der Waals forces. The
interplay of elastic and adhesion energies is shown to lead to stacking
disorder and moir\'e structures. Band structure calculations reveal substrate
induced mass terms in graphene which change their sign with the stacking
configuration. The dispersion, absolute band gaps and the real space shape of
the low energy electronic states in the moir\'e structures are discussed. We
find that the absolute band gaps in the moir\'e structures are at least an
order of magnitude smaller than the maximum local values of the mass term. Our
results are in agreement with recent STM experiments.Comment: 8 pages, 8 figures, revised and extended version, to appear in Phys.
Rev.
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