217,792 research outputs found
Non-Abelian statistics in the interference noise of the Moore-Read quantum Hall state
We propose noise oscillation measurements in a double point contact,
accessible with current technology, to seek for a signature of the non-abelian
nature of the \nu=5/2 quantum Hall state. Calculating the voltage and
temperature dependence of the current and noise oscillations, we predict the
non-abelian nature to materialize through a multiplicity of the possible
outcomes: two qualitatively different frequency dependences of the nonzero
interference noise. Comparison between our predictions for the Moore-Read state
with experiments on \nu=5/2 will serve as a much needed test for the nature of
the \nu=5/2 quantum Hall state.Comment: 4 pages, 4 figures v2: typo's corrected, discussions clarified,
references adde
Self-tuning of the cosmological constant
Here, I discuss the cosmological constant (CC) problems, in particular paying
attention to the vanishing cosmological constant. There are three cosmological
constant problems in particle physics. Hawking's idea of calculating the
probability amplitude for our Universe is peaked at CC = 0 which I try to
obtain after the initial inflationary period using a self-tuning model. I
review what has been discussed on the Hawking type calculation, and present a
(probably) correct way to calculate the amplitude, and show that the
Kim-Kyae-Lee self-tuning model allows a finite range of parameters for the CC =
0 to have a singularly large probability, approached from the AdS side.Comment: 12 pages with 8 figure
To steal or not to steal: Firm attributes, legal environment, and valuation
Newly released data on corporate governance and disclosure practices reveal wide within-country variation, with the variation increasing as legal environment gets less investor friendly. This paper examines why firms practice high-quality governance when law does not require it; firm attributes that are related to the quality of governance; how the attributes interact with legal environment; and the relation between firm valuation and corporate governance. A simple model, in which a controlling shareholder trades off private benefits of diversion against costs that vary across countries and time, identifies three relevant firm attributes: investment opportunities, external financing, and ownership structure. Using firm-level governance and transparency data on 859 firms in 27 countries, we find that firms with greater growth opportunities, greater needs for external financing, and more concentrated cash flow rights practice higher-quality governance and disclose more. Moreover, firms that score higher in governance and transparency rankings are valued higher in the stock market. Equally important, all these relations are stronger in countries that are less investor friendly, demonstrating that firms do adapt to poor legal environments to establish efficient governance practices.http://deepblue.lib.umich.edu/bitstream/2027.42/39939/3/wp554.pd
Surplus Angle and Sign-flipped Coulomb Force in Projectable Horava-Lifshitz Gravity
We obtain the static spherically symmetric vacuum solutions of
Horava-Lifshitz gravity theory, imposing the detailed balance condition only in
the UV limit. We find the solutions in two different coordinate systems, the
Painlev\'e-Gullstrand coordinates and the Poincare coordinates, to examine the
consequences of imposing the projectability condition. The solutions in two
coordinate systems are distinct due to the non-relativistic nature of the HL
gravity. In the Painleve-Gullstrand coordinates complying with the
projectability condition, the solution involves an additional integration
constant which yields surplus angle and implies attractive Coulomb force
between same charges.Comment: 13 page
Review of economic evidence in the prevention and early detection of colorectal cancer.
This paper aims to systematically review the cost-effectiveness evidence, and to provide a critical appraisal of the methods used in the model-based economic evaluation of CRC screening and subsequent surveillance. A search strategy was developed to capture relevant evidence published 1999-November 2012. Databases searched were MEDLINE, EMBASE, National Health Service Economic Evaluation (NHS EED), EconLit, and HTA. Full economic evaluations that considered costs and health outcomes of relevant intervention were included. Sixty-eight studies which used either cohort simulation or individual-level simulation were included. Follow-up strategies were mostly embedded in the screening model. Approximately 195 comparisons were made across different modalities; however, strategies modelled were often simplified due to insufficient evidence and comparators chosen insufficiently reflected current practice/recommendations. Studies used up-to-date evidence on the diagnostic test performance combined with outdated information on CRC treatments. Quality of life relating to follow-up surveillance is rare. Quality of life relating to CRC disease states was largely taken from a single study. Some studies omitted to say how identified adenomas or CRC were managed. Besides deterministic sensitivity analysis, probabilistic sensitivity analysis (PSA) was undertaken in some studies, but the distributions used for PSA were rarely reported or justified. The cost-effectiveness of follow-up strategies among people with confirmed adenomas are warranted in aiding evidence-informed decision making in response to the rapidly evolving technologies and rising expectations
Brane gravity, massless bulk scalar and self-tuning of the cosmological constant
We show that a self-tuning mechanism of the cosmological constant could work
in 5D non-compact space-time with a symmetry in the presence of a
massless scalar field. The standard model matter fields live only on the 4D
brane. The change of vacuum energy on the brane (brane cosmological constant)
by, for instance, electroweak and QCD phase transitions, just gives rise to
dynamical shifts of the profiles of the background metric and the scalar field
in the extra dimension, keeping 4D space-time flat without any fine-tuning. To
avoid naked singularities in the bulk, the brane cosmological constant should
be negative. We introduce an additional brane-localized 4D Einstein-Hilbert
term so as to provide the observed 4D gravity with the non-compact extra
dimension. With a general form of brane-localized gravity term allowed by the
symmetries, the low energy Einstein gravity is successfully reproduced on the
brane at long distances. We show this phenomenon explicitly for the case of
vanishing bulk cosmological constant.Comment: 1+15 pages, no figure, Version to appear in PR
Second order quantum corrections to the classical reflection factor of the sinh-Gordon model
The sinh-Gordon model on a half-line with integrable boundary conditions is
considered in low order perturbation theory developed in affine Toda field
theory. The quantum corrections to the classical reflection factor of the model
are studied up to the second order in the difference of the two boundary
parameters and to one loop order in the bulk coupling. It is noticed that the
general form of the second order quantum corrections are consistent with
Ghoshal's formula.Comment: 24 pages and 1 figure. LaTex2
Non-volatile bistability effect based on electrically controlled phase transition in scaled magnetic semiconductor nanostructures
We explore the bistability effect in a dimensionally scaled semiconductor
nanostruncture consisting of a diluted magnetic semiconductor quantum dot (QD)
and a reservoir of itinerant holes separated by a barrier. The bistability
stems from the magnetic phase transition in the QD mediated by the changes in
the hole population. Our calculation shows that when properly designed, the
thermodynamic equilibrium of the scaled structure can be achieved at two
different configurations; i.e., the one with the QD in a ferromagnetic state
with a sufficient number of holes and the other with the depopulated QD in a
paramagnetic state. Subsequently, the parameter window suitable for this
bistability formation is discussed along with the the conditions for the
maximum robustness/non-volatility. To examine the issue of scaling, an
estimation of the bistabiity lifetime is made by considering the thermal
fluctuation in the QD hole population via the spontaneous transitions. A
numerical evaluation is carried out for a typical carrier-mediated magnetic
semiconductor (e.g., GaMnAs) as well as for a hypothetical case of high Curie
temperature for potential room temperature operation.Comment: 9 pages, 7 figure
First order quantum corrections to the classical reflection factor of the sinh-Gordon model
The sinh-Gordon model is restricted to a half-line by boundary conditions
maintaining integrability. A perturbative calculation of the reflection factor
is given to one loop order in the bulk coupling and to first order in the
difference of the two parameters introduced at the boundary, providing a
further verification of Ghoshal's formula. The calculation is consistent with a
conjecture for the general dependence of the reflection factor on the boundary
parameters and the bulk coupling.Comment: 16 pages, 1 figur
Non-Classical Response from Quench-Cooled Solid Helium Confined in Porous Gold
We have investigated the non-classical response of solid 4He confined in
porous gold set to torsional oscillation. When solid helium is grown rapidly,
nearly 7% of the solid helium appears to be decoupled from the oscillation
below about 200 mK. Dissipation appears at temperatures where the decoupling
shows maximum variation. In contrast, the decoupling is substantially reduced
in slowly grown solid helium. The dynamic response of solid helium was also
studied by imposing a sudden increase in the amplitude of oscillation. Extended
relaxation in the resonant period shift, suggesting the emergence of the
pinning of low energy excitations, was observed below the onset temperature of
the non-classical response. The motion of a dislocation or a glassy solid is
restricted in the entangled narrow pores and is not likely responsible for the
period shift and long relaxation
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