Competition between fluctuations and disorder in frustrated magnets

We investigate the effects of impurities on the nature of the phase transition in frustrated magnets, in d=4-epsilon dimensions. For sufficiently small values of the number of spin components, we find no physically relevant stable fixed point in the deep perturbative region (epsilon << 1), contrarily to what is to be expected on very general grounds. This signals the onset of important physical effects.Comment: 4 pages, 3 figures, published versio

ADHM/Nahm Construction of Localized Solitons in Noncommutative Gauge Theories

We study the relationship between ADHM/Nahm construction and ``solution generating technique'' of BPS solitons in noncommutative gauge theories. ADHM/Nahm construction and ``solution generating technique'' are the most strong ways to construct exact BPS solitons. Localized solitons are the solitons which are generated by the ``solution generating technique.'' The shift operators which play crucial roles in ``solution generating technique'' naturally appear in ADHM/Nahm construction and we can construct various exact localized solitons including new solitons: localized periodic instantons (=localized calorons) and localized doubly-periodic instantons. Nahm construction also gives rise to BPS fluxons straightforwardly from the appropriate input Nahm data which is expected from the D-brane picture of BPS fluxons. We also show that the Fourier-transformed soliton of the localized caloron in the zero-period limit exactly coincides with the BPS fluxon.Comment: 30 pages, LaTeX, 3 figures; v3: minor changes, references added; v4: references added, version to appear in PR

Spinning particles in Taub-NUT space

The geodesic motion of pseudo-classical spinning particles in Euclidean Taub-NUT space is analysed. The constants of motion are expressed in terms of Killing-Yano tensors. Some previous results from the literature are corrected.Comment: LaTeX, 8 page

SU(2) Calorons and Magnetic Monopoles

We investigate the self-dual Yang-Mills gauge configurations on $R^3\times S^1$ when the gauge symmetry SU(2) is broken to U(1) by the Wilson loop. We construct the explicit field configuration for a single instanton by the Nahm method and show that an instanton is composed of two self-dual monopoles of opposite magnetic charge. We normalize the moduli space metric of an instanton and study various limits of the field configuration and its moduli space metric.Comment: 17 pages, RevTex, 1 Figur

Sex differences in neurodevelopmental and common mental disorders examined from three epidemiological perspectives.

Sex differences in neurodevelopmental and common mental disorders are a ubiquitous, well-known, though poorly understood phenomenon. This study examined the issue from three epidemiological perspectives: congruence in age of onset, distribution of sex-ratios with respect to age of onset and similarity of comorbidity and risk factor patterns. The analysis was based on data from the population-based PsyCoLaus study (N = 4874, age 35-82 y). Congruence in age of onset and distribution of sex-ratios were examined with the Mann-Whitney test and cluster analysis. The similarity of comorbidity and risk factor patterns, which were represented by 35 variables, was assessed with the Jaccard coefficient and, after factor analysis, with Tucker's congruence coefficient. While age of onset parameters differed little by sex, the sex ratio varied markedly both in early and in late onset disorders. Moreover, the Jaccard coefficients for most disorders indicated that the similarity of comorbidity and further association patterns was low. Similarly, Tucker's congruence coefficient remained below the range of fair similarity in all factor combinations. In sum, sex differences in common mental disorders were impressively reflected by diverging sex ratios and comorbidity / risk factor patterns. This outcome supports the notion that most mental disorders need a sex-specific etiopathogenetic understanding

Hamiltonian dynamics and spectral theory for spin-oscillators

We study the Hamiltonian dynamics and spectral theory of spin-oscillators. Because of their rich structure, spin-oscillators display fairly general properties of integrable systems with two degrees of freedom. Spin-oscillators have infinitely many transversally elliptic singularities, exactly one elliptic-elliptic singularity and one focus-focus singularity. The most interesting dynamical features of integrable systems, and in particular of spin-oscillators, are encoded in their singularities. In the first part of the paper we study the symplectic dynamics around the focus-focus singularity. In the second part of the paper we quantize the coupled spin-oscillators systems and study their spectral theory. The paper combines techniques from semiclassical analysis with differential geometric methods.Comment: 32 page

Constructing Self-Dual Strings

We present an ADHMN-like construction which generates self-dual string solutions to the effective M5-brane worldvolume theory from solutions to the Basu-Harvey equation. Our construction finds a natural interpretation in terms of gerbes, which we develop in some detail. We also comment on a possible extension to stacks of multiple M5-branes.Comment: 1+19 pages, presentation improved, minor corrections, published versio

D0-D4 brane tachyon condensation to a BPS state and its excitation spectrum in noncommutative super Yang-Mills theory

We investigate the D0-D4-brane system for different B-field backgrounds including the small instanton singularity in noncommutative SYM theory. We discuss the excitation spectrum of the unstable state as well as for the BPS D0-D4 bound state. We compute the tachyon potential which reproduces the complete mass defect. The relevant degrees of freedom are the massless (4,4) strings. Both results are in contrast with existing string field theory calculations. The excitation spectrum of the small instanton is found to be equal to the excitation spectrum of the fluxon solution on R^2_theta x R which we trace back to T-duality. For the effective theory of the (0,0) string excitations we obtain a BFSS matrix model. The number of states in the instanton background changes significantly when the B-field becomes self-dual. This leads us to the proposal of the existence of a phase transition or cross over at self-dual B-field.Comment: a4 11pt Latex2e 40 pages; v2: typos fixed, refined comments on renormalisation, refs added, v3: ref added, version publishe

Four dimensional "old minimal" N=2 supersymmetrization of R^4

We write in superspace the lagrangian containing the fourth power of the Weyl tensor in the "old minimal" d=4, N=2 supergravity, without local SO(2) symmetry. Using gauge completion, we analyze the lagrangian in components. We find out that the auxiliary fields which belong to the Weyl and compensating vector multiplets have derivative terms and therefore cannot be eliminated on-shell. Only the auxiliary fields which belong to the compensating nonlinear multiplet do not get derivatives and could still be eliminated; we check that this is possible in the leading terms of the lagrangian. We compare this result to the similar one of "old minimal" N=1 supergravity and we comment on possible generalizations to other versions of N=1,2 supergravity.Comment: 31 pages, no figures. Minor corrections. Details of the full calculation included as an appendix. Reference adde

Predictions for the 4 GeV TJNAF inclusive electron scattering experiment and for FSI effects in EMC ratios

We express nuclear structure functions $F_i^A$ as generalized convolutions of the structure function of a nucleon and of a nucleus, composed of point-nucleons. In computations of the latter we include Final State Interactions and results for $F_2^A$ are compared with a few directly measured data on C and Fe. The above $F_i^A$ are primarily used for predictions of the TJNAF 89-008 inclusive scattering experiment of 4 GeV electrons on various targets. Those cover a broad angular, and correspondingly wide $x,Q^2$ range, where the nucleon-inelastic part dominates large sections of the covered kinematics. The same model has been applied to the study of hitherto neglected Final State Interaction effects in the nuclear component in EMC ratios in the region $0.85\lesssim x\lesssim 0.25$.Comment: 12 page