6,842 research outputs found
Capital Gains Realizations of the Rich and Sophisticated
This paper attempts to bring theoretical and empirical research on capital gains realization behavior closer together by considering whether investors who appear to engage more in strategic tax avoidance activity also respond differently to tax rates. We find that such investors exhibit significantly smaller responses to permanent tax rate changes than other investors. Put another way, a larger part of their response to capital gains tax rates reflects timing, consistent with their closer adherence to tax avoidance strategies emphasizing arbitrage based on tax rate differentials. This finding holds for two alternative specifications of realization behavior, one of which suggests larger permanent responses to capital gains tax rates than those of previous panel studies.
Tax Loss Carryforwards and Corporate Tax Incentives
This paper investigates the extent to which loss-offset constraints affect corporate tax incentives. Using data gathered from corporate annual reports, we estimate that in 1984 fifteen percent of the firms in the nonfinancial corporate sector had tax loss carryforwards. When weighted by their market value, however, these firms account for less than three percent of this sector, suggesting that loss carryforwards are concentrated among small firms and affect relatively few large corporations. For those firms with loss carryforwards, however, the incentive effects of the corporate income tax may differ significantly from those facing taxable firms. We demonstrate this by calculating the effective tax rates on equipment and structures for both types of firms. Our results suggest that firms which are currently taxable have a substantially greater incentive for equipment investment than firms with loss carryforwards, but that loss carryforwards have a relatively smaller effect on the tax incentive for investing in structures. Overall, firms with loss carryforwards receive a smaller investment stimulus than taxable firms.
Domain Patterns in the Microwave-Induced Zero-Resistance State
It has been proposed that the microwave-induced ``zero-resistance''
phenomenon, observed in a GaAs two-dimensional electron system at low
temperatures in moderate magnetic fields, results from a state with multiple
domains, in which a large local electric field \bE(\br) is oriented in
different directions. We explore here the questions of what may determine the
domain arrangement in a given sample, what do the domains look like in
representative cases, and what may be the consequences of domain-wall
localization on the macroscopic dc conductance. We consider both effects of
sample boundaries and effects of disorder, in a simple model, which has a
constant Hall conductivity, and is characterized by a Lyapunov functional.Comment: 19 pages, 5 figures; submitted to a special issue of Journal of
Statistical Physics, in honor of P. C. Hohenberg and J. S. Lange
Quantum phase transitions in the Fermi-Bose Hubbard model
We propose a multi-band Fermi-Bose Hubbard model with on-site fermion-boson
conversion and general filling factor in three dimensions. Such a Hamiltonian
models an atomic Fermi gas trapped in a lattice potential and subject to a
Feshbach resonance. We solve this model in the two state approximation for
paired fermions at zero temperature. The problem then maps onto a coupled
Heisenberg spin model. In the limit of large positive and negative detuning,
the quantum phase transitions in the Bose Hubbard and Paired-Fermi Hubbard
models are correctly reproduced. Near resonance, the Mott states are given by a
superposition of the paired-fermion and boson fields and the Mott-superfluid
borders go through an avoided crossing in the phase diagram.Comment: 4 pages, 3 figure
Effective single-band models for strongly interacting fermions in an optical lattice
To test effective Hamiltonians for strongly interacting fermions in an
optical lattice, we numerically find the energy spectrum for two fermions
interacting across a Feshbach resonance in a double well potential. From the
spectrum, we determine the range of detunings for which the system can be
described by an effective lattice model, and how the model parameters are
related to the experimental parameters. We find that for a range of strong
interactions the system is well described by an effective model, and the
effective superexchange term, , can be smoothly tuned through zero on either
side of unitarity. Right at and around unitarity, an effective one-band general
Hubbard model is appropriate, with a finite and small on-site energy, due to a
lattice-induced anharmonic coupling between atoms at the scattering threshold
and a weakly bound Feshbach molecule in an excited center of mass state.Comment: 7 pages, 7 figures; minor typos correcte
A Path Intergal Approach to Current
Discontinuous initial wave functions or wave functions with discontintuous
derivative and with bounded support arise in a natural way in various
situations in physics, in particular in measurement theory. The propagation of
such initial wave functions is not well described by the Schr\"odinger current
which vanishes on the boundary of the support of the wave function. This
propagation gives rise to a uni-directional current at the boundary of the
support. We use path integrals to define current and uni-directional current
and give a direct derivation of the expression for current from the path
integral formulation for both diffusion and quantum mechanics. Furthermore, we
give an explicit asymptotic expression for the short time propagation of
initial wave function with compact support for both the cases of discontinuous
derivative and discontinuous wave function. We show that in the former case the
probability propagated across the boundary of the support in time is
and the initial uni-directional current is . This recovers the Zeno effect for continuous detection of a particle
in a given domain. For the latter case the probability propagated across the
boundary of the support in time is and the
initial uni-directional current is . This is an anti-Zeno
effect. However, the probability propagated across a point located at a finite
distance from the boundary of the support is . This gives a decay
law.Comment: 17 pages, Late
Controlling Spin Exchange Interactions of Ultracold Atoms in Optical Lattices
We describe a general technique that allows to induce and control strong
interaction between spin states of neighboring atoms in an optical lattice. We
show that the properties of spin exchange interactions, such as magnitude,
sign, and anisotropy can be designed by adjusting the optical potentials. We
illustrate how this technique can be used to efficiently ``engineer'' quantum
spin systems with desired properties, for specific examples ranging from
scalable quantum computation to probing a model with non-trivial topological
orders that supports exotic non-abelian anyonic excitations.Comment: 5 pages, 2 figures, revte
Tunneling-driven breakdown of the 331 state and the emergent Pfaffian and composite Fermi liquid phases
We examine the possibility of creating the Moore-Read Pfaffian in the lowest
Landau level when the multicomponent Halperin 331 state (believed to describe
quantum Hall bilayers and wide quantum wells at the filling factor )
is destroyed by the increase of tunneling. Using exact diagonalization of the
bilayer Hamiltonian with short-range and long-range (Coulomb) interactions in
spherical and periodic rectangular geometries, we establish that tunneling is a
perturbation that drives the 331 state into a compressible composite Fermi
liquid, with the possibility for an intermediate critical state that possesses
some properties of the Moore-Read Pfaffian. These results are interpreted in
the two-component BCS model for Cauchy pairing with a tunneling constraint. We
comment on the conditions to be imposed on a system with fluctuating density in
order to achieve the stable Pfaffian phase.Comment: 10 pages, 7 figure
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