Phase diagram of an impurity in the spin-1/2 chain: two channel Kondo effect versus Curie law

We consider a magnetic s=1/2 impurity in the antiferromagnetic spin chain as a function of two coupling parameters: the symmetric coupling of the impurity to two sites in the chain $J_1$ and the coupling between the two sites $J_2$. By using field theory arguments and numerical calculations we can identify all possible fixed points and classify the renormalization flow between them, which leads to a non-trivial phase diagram. Depending on the detailed choice of the two (frustrating) coupling strengths, the stable phases correspond either to a decoupled spin with Curie law behavior or to a non-Fermi liquid fixed point with a logarithmically diverging impurity susceptibility as in the two channel Kondo effect. Our results resolve a controversy about the renormalization flow.Comment: 5 pages in revtex format including 4 embedded figures (using epsf). The latest version in PDF format is available from http://fy.chalmers.se/~eggert/papers/phase-diagram.pd

Universal cross-over behavior of a magnetic impurity and consequences for doping in spin-1/2 chains

We consider a magnetic impurity in the antiferromagnetic spin-1/2 chain which is equivalent to the two-channel Kondo problem in terms of the field theoretical description. Using a modification of the transfer-matrix density matrix renormalization group (DMRG) we are able to determine local and global properties in the thermodynamic limit. The cross-over function for the impurity susceptibility is calculated over a large temperature range, which exhibits universal data-collapse. We are also able to determine the local susceptibilities near the impurity, which show an interesting competition of boundary effects. This results in quantitative predictions for experiments on doped spin-1/2 chains, which could observe two-channel Kondo physics directly.Comment: 5 pages in revtex format including 3 embedded figures (using epsf). The latest version in PDF format is available from http://fy.chalmers.se/~eggert/papers/crossover.pdf . Accepted by PR

Physics Possibilities at a Linear Collider

We review some recent studies about the parameter determination of top quarks, W bosons, Higgs bosons, supersymmetric particles and in the ADD model of extra dimensions at a linear collider.Comment: 16 pages, LaTeX, 9 eps figures, invited plenary talk presented by A. Bartl at the "Workshop on High Energy Physics Phenomenology (WHEPP-8)", Indian Institute of Technology, Mumbai, January 5 - 16, 200

Generation of phase-controlled ultraviolet pulses and characterization by a simple autocorrelator setup

A versatile femtosecond ultraviolet (UV) pulse generation, a phase modulation, and a characterization setup for coherent control applications are demonstrated. For high-performance phase control of ultrashort pulses direct in the UV a microelectromechanical-system-based 2D mirror array is applied. Multiple examples for successful phase control of ultrashort UV pulses are given, such as arbitrarily phase tailoring and pulse recompression in open and closed loop schemes. For simple and effective characterization of the generated pulses, a UV autocorrelator based on two-photon absorption in a solar blind photomultiplier is constructed. The effects of space-time coupling on split mirror autocorrelation measurements are addressed and minimized. © 2009 Optical Society of America

A scoping review of health-related stigma outcomes for high-burden diseases in low- and middle-income countries

__Background:__ Stigma is associated with health conditions that drive disease burden in low- and middle-income countries (LMICs), including HIV, tuberculosis, mental health problems, epilepsy, and substance use disorders. However, the literature discussing the relationship between stigma and health outcomes is largely fragmented within disease-specific siloes, thus limiting the identification of common moderators or mechanisms through which stigma potentiates adverse health outcomes as well as the development of broadly relevant stigma mitigation interventions. __Methods:__ We conducted a scoping review to provide a critical overview of the breadth of research on stigma for each of the five aforementioned conditions in LMICs, including their methodological strengths and limitations

Ultrafast Coherent Generation of Hot Electrons Studied via Band-to-Acceptor Luminescence in GaAs

The distribution of hot electrons excited with femtosecond laser pulses is studied via spectrally resolved band-to-acceptor luminescence. Our data demonstrate for the first time that the coherent coupling between the laser pulse and the interband polarization strongly influences the initial carrier distribution. The energetic width of carrier generation is broadened due to rapid phase-breaking scattering events. Theoretical results from a Monte Carlo solution of the semiconductor Bloch equations including on the same kinetic level coherent and incoherent phenomena, are in excellent agreement with the experimental data

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Disclosure of same-sex practices and experiences of healthcare stigma among cisgender men who have sex with men in five sub-Saharan African countries

Background For men who have sex with men (MSM) across sub-Saharan Africa (SSA), disclosure of same-sex practices to family and healthcare workers (HCWs) can facilitate access to HIV prevention services and support, but can also lead to experiences of stigma. Methods We performed mixed-effects regressions on pooled data from MSM in Cameroon, Senegal, Côte d’Ivoire, Lesotho, and eSwatini to assess associations between disclosure and sexual behavior stigma in healthcare contexts; we used logistic regressions to analyze country-specific data. Results Compared to participants who had not disclosed to either family or HCWs, those who had disclosed only to family were more likely to have been gossiped about by HCWs (aOR = 1.70, CI = 1.18, 2.45); the association between having disclosed to family and having felt mistreated in a health center approached, but did not achieve, statistical significance (aOR = 1.56, CI = 0.94, 2.59). Those who had disclosed only to HCWs were more likely to have feared to seek health services (aOR = 1.60, CI = 1.14, 2.25), avoided health services (aOR = 1.74, CI = 1.22, 2.50), and felt mistreated in a health center (aOR = 2.62, CI = 1.43, 4.81). Those who had disclosed to both were more likely to have feared to seek health services (aOR = 1.71, CI = 1.16, 2.52), avoided health services (aOR = 1.59, CI = 1.04, 2.42), been gossiped about by HCWs (aOR = 3.78, CI = 2.38, 5.99), and felt mistreated in a health center (aOR = 3.39, CI = 1.86, 6.20). Country-specific analyses suggested that data from Cameroon drove several of these associations. Conclusions Research to determine the factors driving disclosure’s differential effect on healthcare stigma across contexts is needed. Ultimately, supportive environments enabling safe disclosure is critical to understanding HIV-acquisition risks and informing differentiated HIV-prevention, treatment, and testing services for MSM across SSA

Publisher Correction To: Disclosure of same-sex practices and experiences of healthcare stigma among cisgender men who have sex with men in five sub-Saharan African countries

An amendment to this paper has been published and can be accessed via the original article

Strain-induced pseudomagnetic field and Landau levels in photonic structures

Magnetic effects at optical frequencies are notoriously weak. This is evidenced by the fact that the magnetic permeability of nearly all materials is unity in the optical frequency range, and that magneto-optical devices (such as Faraday isolators) must be large in order to allow for a sufficiently strong effect. In graphene, however, it has been shown that inhomogeneous strains can induce 'pseudomagnetic fields' that behave very similarly to real fields. Here, we show experimentally and theoretically that, by properly structuring a dielectric lattice, it is possible to induce a pseudomagnetic field at optical frequencies in a photonic lattice, where the propagation dynamics is equivalent to the evolution of an electronic wavepacket in graphene. To our knowledge, this is the first realization of a pseudomagnetic field in optics. The induced field gives rise to multiple photonic Landau levels (singularities in the density of states) separated by band gaps. We show experimentally and numerically that the gaps between these Landau levels give rise to transverse confinement of the optical modes. The use of strain allows for the exploration of magnetic effects in a non-resonant way that would be otherwise inaccessible in optics. Employing inhomogeneous strain to induce pseudomagnetism suggests the possibility that aperiodic photonic crystal structures can achieve greater field-enhancement and slow-light effects than periodic structures via the high density-of-states at Landau levels. Generalizing these concepts to other systems beyond optics, for example with matter waves in optical potentials, offers new intriguing physics that is fundamentally different from that in purely periodic structures.Comment: 24 pages including supplementary information section, 4 figure