21,745 research outputs found
The information content of a new observable: the case of the nuclear neutron skin
We address two questions pertaining to the uniqueness and usefulness of a new
observable: (i) Considering the current theoretical knowledge, what novel
information does new measurement bring in? (ii) How can new data reduce
uncertainties of current theoretical models? We illustrate these points by
studying the radius of the neutron distribution of a heavy nucleus, a quantity
related to the equation of state for neutron matter that determines properties
of nuclei and neutron stars. By systematically varying parameters of two
theoretical models and studying the resulting confidence ellipsoid, we quantify
the relationships between the neutron skin and various properties of finite
nuclei and infinite nuclear matter. Using the covariance analysis, we identify
observables and pseudo-observables that correlate, and do not correlate, with
the neutron skin. By adding the information on the neutron radius to the pool
of observables determining the energy functional, we show how precise
experimental determination of the neutron radius in Pb would reduce
theoretical uncertainties on the neutron matter equation of state.Comment: 5 pages, 3 figure
D-string on near horizon geometries and infinite conformal symmetry
We show that the symmetries of effective D-string actions in constant dilaton
backgrounds are directly related to homothetic motions of the background
metric. In presence of such motions, there are infinitely many nonlinearly
realized rigid symmetries forming a loop (or loop like) algebra. Near horizon
(AdS) D3 and D1+D5 backgrounds are discussed in detail and shown to provide 2d
interacting field theories with infinite conformal symmetry.Comment: 5 pages, revtex, no figures; symmetry transformations for BI action
added, coupling of D-string to RR 2-form in D1-D5 background corrected; final
version, to appear in Phys. Rev. Let
Anomaly candidates and invariants of D=4, N=1 supergravity theories
All anomaly candidates and the form of the most general invariant local
action are given for old and new minimal supergravity, including the cases
where additional Yang--Mills and chiral matter multiplets are present.
Furthermore nonminimal supergravity is discussed. In this case local
supersymmetry itself may be anomalous and some of the corresponding anomaly
candidates are given explicitly. The results are obtained by solving the
descent equations which contain the consistency equation satisfied by
integrands of anomalies and invariant actions.Comment: 19 pages, LaTex, NIKHEF-H 93-12, ITP-UH 07/9
El Roque de Los Muchachos Site Characteristics. II. Analysis of Wind, Relative Humidity and Air Pressure
In this paper we present an analysis of wind speed, wind direction, relative
humidity and air pressure taken at TNG, CAMC and NOT at Observatorio del Roque
de Los Muchachos, in the Canary Islands. Data are compared in order to check
local variations and both long term and short term trends of the microclimate.
Furthermore, influence of wind speed on the astronomical seeing is estimated to
the aim to better understand the influence of wide scale parameters on local
meteorological data. The three telescopes show different prevailing wind
direction, wind speed, relative humidity and air pressure confirming
differences in local microclimate. We found that seeing deteriorates when wind
speed is lower than 3.3 m/s. Comparison in terms of wind speed and high
relative humidity (> 90%) shows that TNG seems to have optimal observational
conditions with respect to CAMC and NOT. Air pressure analysis shows that ORM
is dominated by high pressure. Short time variations of pressure anticipate
temperature variations tipically by 2-3 hours, this property vanishes in time
scales higher than some hours and disappear in longer time scales.Comment: 10 pages, 9 figures, accepted for publication in PAS
Buckling instability in type-II superconductors with strong pinning
We predict a novel buckling instability in the critical state of thin type-II
superconductors with strong pinning. This elastic instability appears in high
perpendicular magnetic fields and may cause an almost periodic series of flux
jumps visible in the magnetization curve. As an illustration we apply the
obtained criteria to a long rectangular strip.Comment: Submitted to Phys. Rev. Let
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