Spin-charge separation in the single hole doped Mott antiferromagnet

The motion of a single hole in a Mott antiferromagnet is investigated based on the t-J model. An exact expression of the energy spectrum is obtained, in which the irreparable phase string effect [Phys. Rev. Lett. 77, 5102 (1996)] is explicitly present. By identifying the phase string effect with spin backflow, we point out that spin-charge separation must exist in such a system: the doped hole has to decay into a neutral spinon and a spinless holon, together with the phase string. We show that while the spinon remains coherent, the holon motion is deterred by the phase string, resulting in its localization in space. We calculate the electron spectral function which explains the line shape of the spectral function as well as the ``quasiparticle'' spectrum observed in angle-resolved photoemission experiments. Other analytic and numerical approaches are discussed based on the present framework.Comment: 16 pages, 9 figures; references updated; to appear in Phys. Rev.

Brain choline concentration: early quantitative marker of ischemia and infarct expansion?

Objective: Better prediction of tissue prognosis in acute stroke might improve treatment decisions. We hypothesized that there are metabolic ischemic disturbances measurable non-invasively by proton MR spectroscopy (1HMRS) that occur earlier than any structural changes visible on diffusion tensor imaging (DTI), which may therefore serve for territorial identification of “tissue at risk”. Methods: We performed multi-voxel 1HMRS plus DTI within a maximum of 26 hours, and DTI at three-seven days, after ischemic stroke. We compared choline, lactate, NAA, creatine concentrations in normal-appearing voxels that became infarcted("infarct expansion”), with normal-appearing voxels around the infarct that remained “healthy”(“non-expansion”) on follow-up DTI. Each “infarct expansion” voxel was additionally classified as either “complete infarct expansion”(infarcted tissue on follow-up DTI covered ≥50% of the voxel) or “partial infarct expansion”(<50% of voxel). Results: In 31 patients (NIHSS:0–28) there were 108 infarct "non-expansion” voxels and 113 infarct "expansion” voxels (of which 80 were “complete expansion” and 33 “partial expansion” voxels). Brain choline concentration increased for each change in expansion category from "non-expansion", via "partial expansion" to "complete expansion" (2423, 3843, 4158i.u.; p<0.05). Changes in lactate, NAA and creatine concentrations in expansion category were insignificant although for lactate there was a tendency to such association. Conclusions: Choline concentration measurable with 1HMRS was elevated in peri-ischemic normal-appearing brain that became infarcted by three-seven days. The degree of elevation was associated with the amount of infarct expansion. 1HMRS might identify DTI-normal appearing tissue at risk of conversion to infarction in early stroke

Cosmic-ray strangelets in the Earth's atmosphere

If strange quark matter is stable in small lumps, we expect to find such lumps, called ``strangelets'', on Earth due to a steady flux in cosmic rays. Following recent astrophysical models, we predict the strangelet flux at the top of the atmosphere, and trace the strangelets' behavior in atmospheric chemistry and circulation. We show that several strangelet species may have large abundances in the atmosphere; that they should respond favorably to laboratory-scale preconcentration techniques; and that they present promising targets for mass spectroscopy experiments.Comment: 28 pages, 4 figures, revtex

Understanding service users’ and therapists’ experiences of pharmacological treatment for sexual preoccupation and/or hypersexuality in incarcerated sex offenders

This research comprises two qualitative studies understanding the experiences of 1) convicted sex offenders voluntarily receiving pharmacological treatment to reduce sexual preoccupation and 2) therapists working with these offenders. The studies form part of a research programme evaluating the use of pharmacological treatment with sexual offenders. In study one, semi-structured interviews were conducted with 13 sexual offenders receiving selective serotonin reuptake inhibitors (SSRIs). In study two, interviews were conducted with eight intervention staff with varying levels of experience of working with offenders taking anti-libidinals. Thematic analysis was used and in study one, two main themes emerged: (i) the impact of the pharmacological treatment on prisoners’ daily functioning; (ii) barriers to compliance/engagement. In study two, three main themes emerged: (i) offenders’ reluctance to engage with pharmacological treatment; (ii) challenges for therapists; (iii) pharmacology: ‘just another piece of the puzzle’. Findings are discussed in relation to practice and future research

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe