297,457 research outputs found

### D-XY Critical Behavior in Cuprate Superconductors

We outline the universal and finite temperature critical properties of the
3D-XY model, extended to anisotropic extreme type-II superconductors, as well
as the universal quantum critical properties in 2D. On this basis we review:
(i) the mounting evidence for 3D-XY behavior in optimally doped cuprate
superconductors and the 3D to 2D crossover in the underdoped regime; (ii) the
finite size limitations imposed by inhomogeneities; (iii) the experimental
evidence for a 2D-XY quantum critical point in the underdoped limit, where the
superconductor to insulator transition occurs; (iv) the emerging implications
and constraints for microscopic models.Comment: 5 pages, 6 figure

### Cosmological parameters from combined second- and third-order aperture mass statistics of cosmic shear

We present predictions for cosmological parameter constraints from combined
measurements of second- and third-order statistics of cosmic shear. We define
the generalized third-order aperture mass statistics and show that it
contains much more information about the bispectrum of the projected matter
density than the skewness of the aperture mass. From theoretical models as well
as from LCDM ray-tracing simulations, we calculate and and
their dependence on cosmological parameters. The covariances including shot
noise and cosmic variance of M_ap^2, M_ap^3 and their cross-correlation are
calculated using ray-tracing simulations. We perform an extensive Fisher matrix
analysis, and for various combinations of cosmological parameters, we predict
1-sigma-errors corresponding to measurements from a deep 29 square degree
cosmic shear survey. Although the parameter degeneracies can not be lifted
completely, the (linear) combination of second- and third-order aperture mass
statistics reduces the errors significantly. The strong degeneracy between
Omega_m and sigma_8, present for all second-order cosmic shear measures, is
diminished substantially, whereas less improvement is found for the
near-degenerate pair consisting of the shape parameter Gamma and the spectral
index n_s. Uncertainties in the source galaxy redshift z_0 increase the errors
of all other parameters.Comment: Revised version, 15 pages, 10 figures, in press at A&A. Some changes
were made including an extension of the analysis. Matches the published
versio

### Identifying Transiting Circumbinary Planets

Transiting planets manifest themselves by a periodic dimming of their host
star by a fixed amount. On the other hand, light curves of transiting
circumbinary (CB) planets are expected to be neither periodic nor to have a
single depth while in transit, making BLS [Kovacs et al. 2002] almost
ineffective. Therefore, a modified version for the identification of CB planets
was developed - CB-BLS. We show that using CB-BLS it is possible to find CB
planets in the residuals of light curves of eclipsing binaries (EBs) that have
noise levels of 1% or more. Using CB-BLS will allow to easily harness the
massive ground- and space- based photometric surveys to look for these objects.
Detecting transiting CB planets is expected to have a wide range of
implications, for e.g.: The frequency of CB planets depend on the planetary
formation mechanism - and planets in close pairs of stars provides a most
restrictive constraint on planet formation models. Furthermore, understanding
very high precision light curves is limited by stellar parameters - and since
for EBs the stellar parameters are much better determined, the resultant
planetary structure models will have significantly smaller error bars, maybe
even small enough to challenge theory.Comment: To appear on the IAU Symposium 253 proceedings. 4 pages, 4 figure

### An analogue of the BGG resolution for locally analytic principal series

Let G be a connected reductive quasisplit algebraic group over a field L
which is a finite extension of the p-adic numbers. We construct an exact
sequence modelled on (the dual of) the BGG resolution involving locally
analytic principal series representations for G(L). This leads to an exact
sequence involving spaces of overconvergent p-adic automorphic forms for
certain groups compact modulo centre at infinity.Comment: 36 pages; corrected proof of Theorem 26; extended results to locally
analytic principal series for G(L); cut unnecessary expository materia

### Magnetic field induced 3D to 1D crossover in Sr0:9La0:1CuO2

The effect of the magnetic field on the critical behavior of Sr0:9La0:1CuO2
is explored in terms of reversible magnetization data. As the correlation
length transverse to the magnetic field Hi,applied along the i-axis, cannot
grow beyond the limiting magnetic length LHi, related to the average distance
between vortex lines, one expects a magnetic field induced finite size effect.
Invoking the scaling theory of critical phenomena we provide clear evidence for
this effect. It implies that in type II superconductors there is a 3D to 1D
crossover line Hpi(T). Consequently, below Tc and above Hpi(T) uperconductivity
is confined to cylinders with diameter LHi(1D). Accordingly, there is no
continuous phase transition in the (H,T)-plane along the Hc2-lines as predicted
by the mean-field treatment.Comment: 4 pages, 5 figure

### Magnetic Field induced Dimensional Crossover Phenomena in Cuprate Superconductors and their Implications

We discuss the occurrence of crossing points in the magnetization -
temperature $(m,T$) plane within the framework of critical phenomena. It is
shown that in a two-dimensional superconducting slab of thickness $d_{s}$
$m_{z}(\delta)$ versus temperature $T$ curves measured in different fields
$\mathbf{H} = H(0,\sin (\delta) ,\cos (\delta))$ will cross at the critical
temperature T_c of the slab. In contrast, in a 3D anisotropic bulk
superconductor the crossing point occurs in the plot $m_{z}(\delta)
/H_{z}^{1/2}$ versus $T$. The experimental facts that 2D crossing point
features have been observed in ceramics and in single crystals for $\mathbf{H}$
close to $\mathbf{H} = H(0,0,1)$, but not for $\mathbf{H} = H(0,1,0)$, is
explained in terms of an angle-dependent crossover field separating the regions
where 2D or 3D thermal fluctuations dominate. The measured 2D-crossing point
data are used to estimate one of the fundamental parameters of cuprate
superconductors, the minimum thickness of the slab $(d_{s})$, which remains
superconducting. Our estimates, based on experimental 2D-crossing point data
for single crystals, reveal that this length adopts material dependent values.
Therefore, experimental data for T_c and $\lambda_{\Vert}^{2}(T=0)$, plotted in
terms of T_c versus $1/\lambda_{\Vert}^{2}(T=0)$ will not tend to a straight
line with universal slope as the underdoped limit is approached. Implications
for magnetic torque measurements are also worked out

### Pressure effects on the superconducting properties of YBa_2Cu_4O_8

Measurements of the magnetization under high hydrostatic pressure (up to 10.2
kbar) in YBa_2Cu_4O_8 were carried out. From the scaling analysis of the
magnetization data the pressure induced shifts of the transition temperature
T_c, the volume V and the anisotropy \gamma have been obtained. It was shown
that the pressure induced relative shift of T_c mirrors essentially that of the
anisotropy. This observation uncovers a novel generic property of anisotropic
type II superconductors, that inexistent in the isotropic case.Comment: 4 pages, 3 figure

### Probing inhomogeneities in type II superconductors by means of thermal fluctuations, magnetic fields and isotope effects

Type II superconductors, consisting of superconducting domains embedded in a
normal or insulating matrix, undergo a rounded phase transition. Indeed, the
correlation length cannot grow beyond the spatial extent of the domains.
Accordingly, the thermodynamic properties will exhibit a finite size effect. It
is shown that the specific heat and penetration depth data of a variety of type
II superconductors, including cuprates, exhibit the characteristic properties
of a finite size effect, arising from domains with nanoscale extent. The finite
size scaling analysis reveals essential features of the mechanism. Transition
temperature and superfluidity increase with reduced domain size. The combined
finite size and isotope effects uncover the relevance of local lattice
distortionsComment: 9 pages, 5 figur

### Libraries in Switzerland

Ausgehend von einem historischen Überblick schildert der Beitrag die Entwicklung der Schweizer Bibliotheken in der Zeit von 1970 bis 2010: soziopolitischer Kontext, Struktur des Bibliothekswesen, technischer Wandel, wichtigste Akteure und aktuelle Herausforderungen. Starting with a brief history of libraries in Switzerland, this report focusses on the development of Swiss libraries from 1970 to 2010: socio-political context, structure of the Swiss library sector, change driven by technology, main actors, and challenges at the beginning of the new millennium. Suite à un aperçu historique, l'article décrit le développement des bibliothèques suisses dans la période de 1970 à 2010: le contexte socio-politique, la structure du secteur des bibliothèques, les changements technologiques, les principaux acteurs et les défis actuels

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