39,287 research outputs found
Testing the Equivalence Principle using Atomic Vacuum Energy Shifts
We consider possible tests of the Einstein Equivalence Principle for
quantum-mechanical vacuum energies by evaluating the Lamb shift transition in a
class of non-metric theories of gravity described by the \tmu formalism. We
compute to lowest order the associated red shift and time dilation parameters,
and discuss how (high-precision) measurements of these quantities could provide
new information on the validity of the equivalence principle.Comment: 4 pages, latex, epsf, 1 figur
Measurement of the single top quark cross section in 0.70 fbâ1 of pp collisions with the ATLAS detector
We present the single-top production results carried out with 0.70 fbâ1 of integrated luminosity collected by the ATLAS detector during the 2011 LHC run at 7TeV center of mass. The t-channel production cross section in the
lepton+jets final state and the Wt production cross section in the dilepton final state are measured. An upper limit on the s-channel production cross section at 95% CL is set
Domain Wall Fermions and the Eta Invariant
We extend work by Callan and Harvey and show how the phase of the chiral
fermion determinant in four dimensions is reproduced by zeromodes bound to a
domain wall in five dimensions. The analysis could shed light on the
applicability of zeromode fermions and the vacuum overlap formulation of
Narayanan and Neuberger for chiral gauge theories on the lattice.Comment: uuencoded file with 3 figures; uses macros harvmac, epsf. Revised
discussion of the Chern-Simons form and SU(2) anomaly in section 4, as well
as additional minor change
Optical and near-infrared spectrophotometric properties of Long Period Variables and other luminous red stars
Based on a new and large sample of optical and near-infrared spectra obtained
at the Mount Stromlo and Siding Spring Observatories (Lancon & Wood 1998;
Lancon & Wood, in preparation), spectrophotometric properties of cool oxygen-
and carbon-rich Long Period Variables and supergiants are presented.
Temperatures of oxygen-rich stars are assigned by comparison with synthetic
spectra computed from up-to-date oxygen-rich model atmosphere grids. The
existence of reliable optical and near-infrared temperature indicators is
investigated. A narrow relation between the bolometric correction BC(I) and the
broad-band colour I-J is obtained for oxygen-rich cool stars. The ability of
specific near-infrared indices to separate luminosity classes, atmospheric
chemistry or variability subtypes is discussed. Some comments are also given on
extinction effects, water band strengths in Long Period Variables and the
evaluation of 12CO/13CO ratio in red giants.Comment: 14 pages, 21 figures, Latex, accepted for publication in Astronomy
and Astrophysics main journal. Also available at
http://www-astro.ulb.ac.be/~ralvarez
Bounds on Quantiles in the Presence of Full and Partial Item Nonresponse
Microeconomic surveys are usually subject to the problem of item nonresponse, typically associated with variables like income and wealth, where confidentiality and/or lack of accurate information can affect the response behavior of the individual. Follow up categorical questions can reduce item nonresponse and provide additional partial information on the missing value, hence improving the quality of the data. In this paper we allow item nonresponse to be non-random and extend Manskiâs approach of estimating bounds to identify an upper and lower limit for the parameter of interest (the distribution function or its quantiles). Our extension consists of deriving bounding intervals taking into account all three types of response behavior: full response, partial (categorical) response and full nonresponse. We illustrate the theory by estimating bounds for the quantiles of the distribution of amounts held in savings accounts. We consider worst case bounds which cannot be improved upon without additional assumptions, as well as bounds that follow from different assumptions of monotonicity.item nonresponse;bracket response;bounds and identification
Nonparametric Bounds in the Presence of Item Nonresponse, Unfolding Brackets and Anchoring
Household surveys often suffer from nonresponse on variables such as income, savings or wealth.Recent work by Manski shows how bounds on conditional quantiles of the variable of interest can be derived, allowing for any type of nonrandom item nonresponse.The width between these bounds can be reduced using follow up questions in the form of unfolding brackets for initial item nonrespondents.Recent evidence, however, suggests that such a design is vulnerable to anchoring effects.In this paper Manski's bounds are extended to incorporate the information provided by the bracket respondents allowing for different forms of anchoring.The new bounds are applied to earnings in the 1996 wave of the Health and Retirement Survey.The results show that the categorical questions can be useful to increase precision of the bounds, even if anchoring is allowed for.microeconomics;nonresponse
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