Liquidity Risk in Banking:Is there Herding?

Abstract: Banks individually optimize their liquidity risk management, often neglecting the externalities generated by their choices on the overall risk of the financial system. This is the main argument to support the regulation of liquidity risk. However, there may be incentives, related for instance to the role of the lender of last resort, for banks to optimize their choices not strictly at the individual level, but engaging instead in collective risk taking strategies, which may intensify systemic risk. In this paper we look for evidence of such herding behaviors, with an emphasis on the period preceding the global financial crisis. Herding is significant only among the largest banks, after adequately controlling for relevant endogeneity problems associated with the estimation of peer effects. This result suggests that the regulation of systemically important financial institutions may play an important role in mitigating this specific component of liquidity risk

Breakdown of the perturbative renormalization group for S >= 1 random antiferromagnetic spin chains

We investigate the application of a perturbative renormalization group (RG) method to random antiferromagnetic Heisenberg chains with arbitrary spin size. At zero temperature we observe that initial arbitrary probability distributions develop a singularity at J=0, for all values of spin S. When the RG method is extended to finite temperatures, without any additional assumptions, we find anomalous results for S >= 1. These results lead us to conclude that the perturbative scheme is not adequate to study random chains with S >= 1. Therefore a random singlet phase in its more restrictive definition is only assured for spin-1/2 chains.Comment: 5 pages, 3 figures. To appear in Physical Review

Exact time dependent Hopf solitons in 3+1 dimensions

We construct an infinite number of exact time dependent soliton solutions, carrying non-trivial Hopf topological charges, in a 3+1 dimensional Lorentz invariant theory with target space S^2. The construction is based on an ansatz which explores the invariance of the model under the conformal group SO(4,2) and the infinite dimensional group of area preserving diffeomorphisms of S^2. The model is a rare example of an integrable theory in four dimensions, and the solitons may play a role in the low energy limit of gauge theories.Comment: 4 pages revtex, 2 eps figures, replaced with one reference adde

Corrections to scaling for diffusion in disordered media

We study the diffusion of a particle in a d-dimensional lattice where disorder arises from a random distribution of waiting times associated with each site of the lattice. Using scaling arguments we derive, in addition to the leading asymptotic behaviour, the correction-to-scaling terms for the mean square displacement. We also perform detailed Monte Carlo simulations for one, two and three dimensions which give results in substantial agreement with the scaling argument predictions

High domain wall velocities induced by current in ultrathin Pt/Co/AlOx wires with perpendicular magnetic anisotropy

Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with perpendicular magnetic anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer-scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j less than or equal to 1.5 x 10^12 A/m^2), the DW motion obeys a creep law. At higher current density (j = 1.8 x 10^12 A/m^2), zero-field average DW velocities up to 130 +/- 10 m/s were recorded.Comment: Minor changes to Fig. 1(b) and text, correcting for the fact that domain walls were subsequently found to move counter to the electron flow. References update

Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al_2\_2O_3\_3/Co magnetic tunnel junctions

We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer.Comment: 8 Pages, 7 Figure

Dynamics of magnetic domain wall motion after nucleation: Dependence on the wall energy

The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small.Comment: Accepted for publication in Physical Review Letter

Contributions to the phylogeny of the haplolepideous mosses

The haplolepideous mosses (Dicranidae) comprise about 4000 species distributed over a wide range of habitats, with great gametophytic and sporophytic morphological variation. Their monophyly is well supported by the results of several molecular phylogenetic studies, which shed light on their relationships and circumscriptions, and thus also contributed to identify many remaining problems. Dicranidae ordinal classification is not congruent with current relationship hypotheses and is not supported by morphology. Morphological circumscriptions of some families do not correspond to monophyletic groups. Furthermore, the monophyly of many families and genera with weak morphological circumscriptions remains to be tested. In this thesis, systematics and relationships of the leucobryoid mosses and some families and genera segregated from the former Dicranaceae s.l. were studied using molecular phylogenetic methods. 37 out of the 38 haplolepideous moss families were represented by markers from the three genomes (nrITS, nad5, trnS-trnF, atpB-rbcL). Phylogenetic reconstructions were based on maximum parsimony, maximum likelihood, and Bayesian inference. Ancestral state reconstructions, phylogenetic network analysis (NeighborNet), and relationship hypothesis testing (Shimodaira-Hasegawa test) were performed to contribute to the interpretation of the results of the phylogenetic reconstructions. Morphological circumscriptions were evaluated and improved whenever possible, in line with the results of all analyses performed.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES, Brazil; Alberta Mennega Stitching, The NetherlandsNaturali