325 research outputs found
On the Perils of Security Pricing by Financial Intermediaries: The Case of Open-End Mutual Funds
There are many instances where financial claims trade at prices set by intermediaries. Pricing by an intermediary introduces the potential for economic distortions from innumerable sources. As one example, we show that nonsynchronous-trading generates predictable, readily exploitable, changes in mutual fund-share prices (NAV). The exploitation of predictable changes in mutual fund NAVs involved a wealth transfer from buy-and-hold fund investors to active fund traders and is costly to all fund investors. A simple modification to the mutual fund pricing algorithm eliminates much of this predictability, but nonsynchronous trading is just one of the issues intermediaries face when setting prices.
de Sitter thermodynamics and the braneworld
The de Sitter thermodynamics of cosmological models with a modified Friedmann
equation is considered, with particular reference to high-energy
Randall-Sundrum and Gauss-Bonnet braneworlds. The Friedmann equation can be
regarded as the first law of thermodynamics of an effective gravitational
theory in quasi de Sitter spacetime. The associated entropy provides some
selection rules for the range of the parameters of the models, and is proposed
for describing tunneling processes in the class of high-energy gravities under
consideration.Comment: 16 pages JHEP style, no figures. v2: references added; v3: typo
corrected in Eq.(3.1), supersedes published versio
Localized Tachyons and the Quantum McKay Correspondence
The condensation of closed string tachyons localized at the fixed point of a
C^d/\Gamma orbifold can be studied in the framework of renormalization group
flow in a gauged linear sigma model. The evolution of the Higgs branch along
the flow describes a resolution of singularities via the process of tachyon
condensation. The study of the fate of D-branes in this process has lead to a
notion of a ``quantum McKay correspondence.'' This is a hypothetical
correspondence between fractional branes in an orbifold singularity in the
ultraviolet with the Coulomb and Higgs branch branes in the infrared. In this
paper we present some nontrivial evidence for this correspondence in the case
C^2/Z_n by relating the intersection form of fractional branes to that of
``Higgs branch branes,'' the latter being branes which wrap nontrivial cycles
in the resolved space.Comment: 25 pages; harvma
Type 0A 2D Black Hole Thermodynamics and the Deformed Matrix Model
Recently, it has been proposed that the deformed matrix model describes a
two-dimensional type 0A extremal black hole. In this paper, the thermodynamics
of 0A charged non-extremal black holes is investigated. We observe that the
free energy of the deformed matrix model to leading order in 1/q can be seen to
agree to that of the extremal black hole. We also speculate on how the deformed
matrix model is able to describe the thermodynamics of non-extremal black
holes.Comment: 12 page
Open String Star as a Continuous Moyal Product
We establish that the open string star product in the zero momentum sector
can be described as a continuous tensor product of mutually commuting two
dimensional Moyal star products. Let the continuous variable parametrize the eigenvalues of the Neumann matrices; then the
noncommutativity parameter is given by .
For each , the Moyal coordinates are a linear combination of even
position modes, and the Fourier transform of a linear combination of odd
position modes. The commuting coordinate at is identified as the
momentum carried by half the string. We discuss the relation to Bars' work, and
attempt to write the string field action as a noncommutative field theory.Comment: 30 pages, LaTeX. One reference adde
Ultracold molecules for quantum simulation: rotational coherence in CaF and RbCs
Polar molecules offer a new platform for quantum simulation of systems with long-range interactions, based on the electrostatic interaction between their electric dipole moments. Here, we report the development of coherent quantum state control using microwave fields in CaF and RbCs molecules, a crucial ingredient for many quantum simulation applications. We perform Ramsey interferometry measurements with fringe spacings of and investigate the dephasing time of a superposition of and rotational states when the molecules are confined. For both molecules, we show that a judicious choice of molecular hyperfine states minimises the impact of spatially varying transition-frequency shifts across the trap. For magnetically trapped CaF we use a magnetically insensitive transition and observe a coherence time of 0.61(3)~ms. For optically trapped RbCs we exploit an avoided crossing in the AC Stark shifts and observe a maximum coherence time of 0.75(6)~ms
Branes, Instantons, And Taub-NUT Spaces
ALE and Taub-NUT (or ALF) hyper-Kahler four-manifolds can be naturally
constructed as hyper-Kahler quotients. In the ALE case, this construction has
long been understood in terms of D-branes; here we give a D-brane derivation in
the Taub-NUT case. Likewise, instantons on ALE spaces and on Taub-NUT spaces
have ADHM-like constructions related to hyper-Kahler quotients. Here we refine
the analysis in the Taub-NUT case by making use of a D-brane probe, and give an
application to M-theory.Comment: 63 p
- …