Finite covers of random 3-manifolds

A 3-manifold is Haken if it contains a topologically essential surface. The Virtual Haken Conjecture posits that every irreducible 3-manifold with infinite fundamental group has a finite cover which is Haken. In this paper, we study random 3-manifolds and their finite covers in an attempt to shed light on this difficult question. In particular, we consider random Heegaard splittings by gluing two handlebodies by the result of a random walk in the mapping class group of a surface. For this model of random 3-manifold, we are able to compute the probabilities that the resulting manifolds have finite covers of particular kinds. Our results contrast with the analogous probabilities for groups coming from random balanced presentations, giving quantitative theorems to the effect that 3-manifold groups have many more finite quotients than random groups. The next natural question is whether these covers have positive betti number. For abelian covers of a fixed type over 3-manifolds of Heegaard genus 2, we show that the probability of positive betti number is 0. In fact, many of these questions boil down to questions about the mapping class group. We are lead to consider the action of mapping class group of a surface S on the set of quotients pi_1(S) -> Q. If Q is a simple group, we show that if the genus of S is large, then this action is very mixing. In particular, the action factors through the alternating group of each orbit. This is analogous to Goldman's theorem that the action of the mapping class group on the SU(2) character variety is ergodic.Comment: 60 pages; v2: minor changes. v3: minor changes; final versio

Direct-Acting Antiviral Hepatitis C Treatment Cascade and Barriers to Treatment Initiation among US Men and Women with and without HIV

Background: People with HIV are disproportionately coinfected with hepatitis C virus (HCV) and experience accelerated liver-related mortality. Direct-acting antivirals (DAAs) yield high sustained virologic response (SVR) rates, but uptake is suboptimal. This study characterizes the DAA-era HCV treatment cascade and barriers among US men and women with or at risk for HIV. Methods: We constructed HCV treatment cascades using the Women's Interagency HIV Study (women, 6 visits, 2015-2018, n=2447) and Multicenter AIDS Cohort Study (men, 1 visit, 2015-2018, n=2221). Cascades included treatment-eligible individuals (ie, HCV RNA-positive or reported DAAs). Surveys captured self-reported clinical (eg, CD4), patient (eg, missed visits), system (eg, appointment access), and financial/insurance barriers. Results: Of 323/92 (women/men) treatment eligible, most had HIV (77%/70%); 69%/63% were black. HIV-positive women were more likely to attain cascade outcomes than HIV-negative women (39% vs 23% initiated, 21% vs 12% SVR); similar discrepancies were noted for men. Black men and substance users were treated less often. Women initiating treatment (vs not) reported fewer patient barriers (14%/33%). Among men not treated, clinical barriers were prevalent (53%). Conclusions: HIV care may facilitate HCV treatment linkage and barrier navigation. HIV-negative individuals, black men, and substance users may need additional support. Clinical trials registration: NCT00000797 (Women's Interagency HIV Study); NCT00046280 (Multicenter AIDS Cohort Study)

Associations between Medicare Part D and Out-of-Pocket Spending, HIV Viral Load, Adherence, and ADAP Use in Dual Eligibles with HIV

Background: The implementation of Medicare part D on January 1, 2006 required all adults who were dually enrolled in Medicaid and Medicare (dual eligibles) to transition prescription drug coverage from Medicaid to Medicare part D. Changes in payment systems and utilization management along with the loss of Medicaid protections had the potential to disrupt medication access, with uncertain consequences for dual eligibles with human immunodeficiency virus (HIV) who rely on consistent prescription coverage to suppress their HIV viral load (VL). Objective: To estimate the effect of Medicare part D on self-reported out-of-pocket prescription drug spending, AIDS Drug Assistance Program (ADAP) use, antiretroviral adherence, and HIV VL suppression among dual eligibles with HIV. Methods: Using 2003–2008 data from the Women’s Interagency HIV Study, we created a propensity score–matched cohort and used a difference-in-differences approach to compare dual eligibles’ outcomes pre-Medicare and post-Medicare part D to those enrolled in Medicaid alone. Results: Transition to Medicare part D was associated with a sharp increase in the proportion of dual eligibles with self-reported out-of-pocket prescription drug costs, followed by an increase in ADAP use. Despite the increase in out-of-pocket costs, both adherence and HIV VL suppression remained stable. Conclusions: Medicare part D was associated with increased out-of-pocket spending, although the increased spending did not seem to compromise antiretroviral therapy adherence or HIV VL suppression. It is possible that increased ADAP use mitigated the increase in out-of-pocket spending, suggesting successful coordination between Medicare part D and ADAP as well as the vital role of ADAP during insurance transitions

Spin dynamics in semiconductors

This article reviews the current status of spin dynamics in semiconductors which has achieved a lot of progress in the past years due to the fast growing field of semiconductor spintronics. The primary focus is the theoretical and experimental developments of spin relaxation and dephasing in both spin precession in time domain and spin diffusion and transport in spacial domain. A fully microscopic many-body investigation on spin dynamics based on the kinetic spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published in Physics Reports

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