3,091 research outputs found
Local or state? Evidence on bank market size using branch prices
With the elimination of state laws against branching, banks can now compete across states. They are no longer limited to competing in local markets, defined by the Federal Reserve as metropolitan statistical areas or small groups of rural counties. Accordingly, a "local or state?" debate over market size is taking place among researchers, with some arguing that banking markets are statewide and others contending that they remain local. This article contributes to the debate with a novel, arguably better, indicator of market size: bank branch prices, as opposed to bank deposit rates. The pattern of branch price data suggests that banking markets are not necessarily local. The authors find that branch prices in ten northeast states over the 1990s are more closely correlated with bank concentration at the state level than at the local level, consistent with the "state-market" argument. However, they caution that the relationship is not completely robust; it depends partly on how the data are parsed. Further study using a larger set of branch price data will help settle the debate more definitively.Banking market ; Branch banks ; Bank competition
NMR relaxation rate in non-centrosymmetric superconductors
The spin-lattice relaxation rate of nuclear magnetic resonance in a clean
superconductor without inversion center is calculated for arbitrary pairing
symmetry and band structure, in the presence of strong spin-orbit coupling.Comment: 4 page
Using Josephson junctions to determine the pairing state of superconductors without crystal inversion symmetry
Theoretical studies of a planar tunnel junction between two superconductors
with antisymmetric spin-orbit coupling are presented. The half-space Green's
function for such a superconductor is determined. This is then used to derive
expressions for the dissipative current and the Josephson current of the
junction. Numerical results are presented in the case of the Rashba spin-orbit
coupling, relevant to the much studied compound CePtSi. Current-voltage
diagrams, differential conductance and the critical Josephson current are
presented for different crystallographic orientations and different weights of
singlet and triplet components of the pairing state. The main conclusion is
that Josephson junctions with different crystallographic orientations may
provide a direct connection between unconventional pairing in superconductors
of this kind and the absence of inversion symmetry in the crystal.Comment: 16 pages, 10 figure
On the spin susceptibility of noncentrosymmetric superconductors
We calculate the spin susceptibility of a superconductor without inversion
symmetry, both in the clean and disordered cases. The susceptibility has a
large residual value at zero temperature, which is further enhanced in the
presence of scalar impurities.Comment: 12 pages, 3 figure
Phases of dual superconductivity and confinement in softly broken N=2 supersymmetric Yang-Mills theories
We study the electric flux tubes that undertake color confinement in N=2
supersymmetric Yang-Mills theories softly broken down to N=1 by perturbing with
the first two Casimir operators. The relevant Abelian Higgs model is not the
standard one due to the presence of an off-diagonal coupling among different
magnetic U(1) factors. We perform a preliminary study of this model at a
qualitative level. BPS vortices are explicitely obtained for particular values
of the soft breaking parameters. Generically however, even in the ultrastrong
scaling limit, vortices are not critical but live in a "hybrid" type II phase.
Also, ratios among string tensions are seen to follow no simple pattern. We
examine the situation at the half Higgsed vacua and find evidence for solutions
with the behaviour of superconducting strings. In some cases they are solutions
to BPS equations.Comment: 15 pages, 1 figure, revtex; v2: typos corrected, final versio
Supersymmetric Electroweak Cosmic Strings
We study the connection between supersymmetry and a topological bound
in a two-Higgs-doublet system with an gauge group. We derive the Bogomol'nyi equations from
supersymmetry considerations showing that they hold provided certain conditions
on the coupling constants, which are a consequence of the huge symmetry of the
theory, are satisfied. Their solutions, which can be interpreted as electroweak
cosmic strings breaking one half of the supersymmetries of the theory, are
studied. Certain interesting limiting cases of our model which have recently
been considered in the literature are finally analyzed.Comment: 20 pages, RevTe
Helical vortex phase in the non-centrosymmetric CePt_3Si
We consider the role of magnetic fields on the broken inversion
superconductor CePt_3Si. We show that upper critical field for a field along
the c-axis exhibits a much weaker paramagnetic effect than for a field applied
perpendicular to the c-axis. The in-plane paramagnetic effect is strongly
reduced by the appearance of helical structure in the order parameter. We find
that to get good agreement between theory and recent experimental measurements
of H_{c2}, this helical structure is required. We propose a Josephson junction
experiment that can be used to detect this helical order. In particular, we
predict that Josephson current will exhibit a magnetic interference pattern for
a magnetic field applied perpendicular to the junction normal. We also discuss
unusual magnetic effects associated with the helical order.Comment: 5 pages, 2 figures, Accepted as Phys Rev. Lette
Excitation of spin waves on a cylindrical semiconductor heterostructure with Rashba spin-orbit interaction
Elementary excitations in a paramagnetic semiconductor quantum well confined
to a cylindrical surface are theoretically studied on the basis of coupled
spin-charge drift-diffusion equations. The electric-field-mediated eigenmodes
are optically excited by an oscillating interference pattern, which induces a
current in the outer circuit. For a cylinder with a given radius, sharp
resonances are predicted to occur in the steady-state current response, which
are due to weakly damped spin remagnetization waves.Comment: 7 pages, 1figur
High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: part 2, photon noise theory
High-resolution broadband spectroscopy at near-infrared (NIR) wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar, with the TEDI interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec NIR echelle spectrograph. These are the first multidelay EDI demonstrations on starlight. We demonstrated very high (10×) resolution boost and dramatic (20× or more) robustness to point spread function wavelength drifts in the native spectrograph. Data analysis, results, and instrument noise are described in a companion paper (part 1). This part 2 describes theoretical photon limited and readout noise limited behaviors, using simulated spectra and instrument model with noise added at the detector. We show that a single interferometer delay can be used to reduce the high frequency noise at the original resolution (1× boost case), and that except for delays much smaller than the native response peak half width, the fringing and nonfringing noises act uncorrelated and add in quadrature. This is due to the frequency shifting of the noise due to the heterodyning effect. We find a sum rule for the noise variance for multiple delays. The multiple delay EDI using a Gaussian distribution of exposure times has noise-to-signal ratio for photon-limited noise similar to a classical spectrograph with reduced slitwidth and reduced flux, proportional to the square root of resolution boost achieved, but without the focal spot limitation and pixel spacing Nyquist limitations. At low boost (∼1×) EDI has ∼1.4× smaller noise than conventional, and at >10× boost, EDI has ∼1.4× larger noise than conventional. Readout noise is minimized by the use of three or four steps instead of 10 of TEDI. Net noise grows as step phases change from symmetrical arrangement with wavenumber across the band. For three (or four) steps, we calculate a multiplicative bandwidth of 1.8:1 (2.3:1), sufficient to handle the visible band (400 to 700 nm, 1.8:1) and most of TripleSpec (2.6:1)
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