12,533 research outputs found
SU(2) gauge theory of gravity with topological invariants
The most general gravity Lagrangian in four dimensions contains three
topological densities, namely Nieh-Yan, Pontryagin and Euler, in addition to
the Hilbert-Palatini term. We set up a Hamiltonian formulation based on this
Lagrangian. The resulting canonical theory depends on three parameters which
are coefficients of these terms and is shown to admit a real SU(2) gauge
theoretic interpretation with a set of seven first-class constraints. Thus, in
addition to the Newton's constant, the theory of gravity contains three
(topological) coupling constants, which might have non-trivial imports in the
quantum theory.Comment: Based on a talk at Loops-11, Madrid, Spain; To appear in Journal of
Physics: Conference Serie
Sealed bid second price auctions with discrete bids
A single item is sold to two bidders by way of a sealed bid second price auction in which bids are restricted to a set of discrete values. Restricting attention to symmetric pure strategy behavior on the part of bidders, a unique equilibrium exists. When following these equilibrium strategies bidders may bid strictly above or below their valuation, implying that the item may be awarded to a bidder other than the high valuation bidder. In an auction with two acceptable bids, the expected revenue of the seller may be maximized by a high bid level not equal to the highest possible bidder valuation and may exceed the expected revenue from an analogous second price auction with continuous bidding (and no reserve price). With three acceptable bids, a revenue maximizing seller may choose unevenly spaced bids. With an arbitrary number of evenly spaced bids, as the number of acceptable bids is increased, the expected revenue of the seller and the probability of ex post inefficiency both may either increase or decrease
Controlling quantum critical dynamics of isolated systems
Controlling the non adiabatic dynamics of isolated quantum systems driven
through a critical point is of interest in a variety of fields ranging from
quantum simulation to finite-time thermodynamics. We briefly review the
different methods for designing protocols which minimize excitation (defect)
production in a closed quantum critical system driven out of equilibrium. We
chart out the role of specific driving schemes for this procedure, point out
their experimental relevance, and discuss their implementation in the context
of ultracold atom and spin systems.Comment: Second version of invited review article submitted to EPJ-ST.
References added, typos corrected. 3 figures, 14 p
The Semiclassical Limit for and Gauge Theory on the Torus
We prove that for and quantum gauge theory on a torus,
holonomy expectation values with respect to the Yang-Mills measure d\mu_T(\o)
=N_T^{-1}e^{-S_{YM}(\o)/T}[{\cal D}\o] converge, as , to
integrals with respect to a symplectic volume measure on the moduli
space of flat connections on the bundle. These moduli spaces and the symplectic
structures are described explicitly.Comment: 18 page
Fock spaces corresponding to positive definite linear transformations
Suppose is a positive real linear transformation on a finite dimensional
complex inner product space . The reproducing kernel for the Fock space of
square integrable holomorphic functions on relative to the Gaussian measure
is described
in terms of the holomorphic--antiholomorphic decomposition of the linear
operator . Moreover, if commutes with a conjugation on , then a
restriction mapping to the real vectors in is polarized to obtain a
Segal--Bargmann transform, which we also study in the Gaussian-measure setting
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