Charge orders, magnetism and pairings in the cuprate superconductors

We review the recent developments in the field of cuprate superconductors with the special focus on the recently observed charge order in the underdoped compounds. We introduce new theoretical developments following the study of the antiferromagnetic (AF) quantum critical point (QCP) in two dimensions, in which preemptive orders in the charge and superconducting (SC) sectors emerged, that are in turn related by an SU(2) symmetry. We consider the implications of this proliferation of orders in the underdoped region, and provide a study of the type of fluctuations which characterize the SU(2) symmetry. We identify an intermediate energy scale where the SU(2) pairing fluctuations are dominant and argue that they are unstable towards the formation of a Resonant Peierls Excitonic (RPE) state at the pseudogap (PG) temperature $T^{*}$. We discuss the implications of this scenario for a few key experiments.Comment: 16 pages, 17 figure

Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black Widow Pulsar PSR B1957+20

The most massive neutron stars constrain the behavior of ultra-dense matter, with larger masses possible only for increasingly stiff equations of state. Here, we present evidence that the black widow pulsar, PSR B1957+20, has a high mass. We took spectra of its strongly irradiated companion and found an observed radial-velocity amplitude of K_obs=324+/-3 km/s. Correcting this for the fact that, due to the irradiation, the center of light lies inward relative to the center of mass, we infer a true radial-velocity amplitude of K_2=353+/-4 km/s and a mass ratio q=M_PSR/M_2=69.2+/-0.8. Combined with the inclination i=65+/-2 deg inferred from models of the lightcurve, our best-fit pulsar mass is M_PSR=2.40+/-0.12 M_sun. We discuss possible systematic uncertainties, in particular in the lightcurve modeling. Taking an upper limit of i<85 deg based on the absence of radio eclipses at high frequency, combined with a conservative lower-limit to the motion of the center of mass, K_2>343 km/s (q>67.3), we infer a lower limit to the pulsar mass of M_PSR>1.66 M_sun.Comment: 7 pages, 3 figures, 1 table, accepted for publication in ApJ; revision includes more detail on the spectral classification and discussion of other recent high neutron-star masse

Hysteretic resistance spikes in quantum Hall ferromagnets without domains

We use spin-density-functional theory to study recently reported hysteretic magnetoresistance \rho_{xx} spikes in Mn-based 2D electron gases [Jaroszy\'{n}ski et al. Phys. Rev. Lett. (2002)]. We find hysteresis loops in our calculated Landau fan diagrams and total energies signaling quantum-Hall-ferromagnet phase transitions. Spin-dependent exchange-correlation effects are crucial to stabilize the relevant magnetic phases arising from distinct symmetry-broken excited- and ground-state solutions of the Kohn-Sham equations. Besides hysteretic spikes in \rho_{xx}, we predict hysteretic dips in the Hall resistance \rho_{xy}. Our theory, without domain walls, satisfactorily explains the recent data.Comment: 4 pages, 4 figures, published version (some changes to the text; same figures as in v1

A call for collaboration: perception of religious and spiritual leaders on mental health (a Portuguese sample)

To assess the relationship and collaborations between mental health professionals and religious and spiritual leaders, eleven representatives of ten different religious affiliations in Portugal participated in this qualitative study. Major findings reported showed that religious leaders perceive themselves as important agents in promoting and preserving their congregants’ mental health, as well as aiding their recovery processes; however this occurs without much referral to or collaboration with mental health professionals. These findings are discussed, as well as why and how a healthy collaboration between mental health professionals and religious leaders can positively impact the psychotherapeutic relationship and clinical outcomes with religious/spiritual clients.info:eu-repo/semantics/acceptedVersio

Group Analysis of the Novikov Equation

We find the Lie point symmetries of the Novikov equation and demonstrate that it is strictly self-adjoint. Using the self-adjointness and the recent technique for constructing conserved vectors associated with symmetries of differential equations, we find the conservation law corresponding to the dilations symmetry and show that other symmetries do not provide nontrivial conservation laws. Then we investigat the invariant solutions

Public geographies II: being organic

This second report on ‘public geographies' considers the diverse, emergent and shifting spaces of engaging with and in public/s. Taking as its focus the more ‘organic’ rather than ‘traditional’ approach to doing public geography, as discussed in the first report, it explores the multiple and unorthodox ways in which engagements across academic-public spheres play out, and what such engagements may mean for geography/ers. The report first explores the role of the internet in ‘enabling conversations', generating a range of opportunities for public geography through websites, wikis, blogs, file-sharing sites, discussion forums and more, thinking critically about how technologies may enable/disable certain kinds of publically engaged activities. It then considers issues of process and praxis: how collaborations with groups/communities/organizations beyond academia are often unplanned, serendipitous encounters that evolve organically into research/learning/teaching endeavours; but also that personal politics/positionality bring an agency to bear upon whether we, as academics, follow the leads we may stumble upon. The report concludes with a provocative question – given that many non-academics appear to be doing some amazing and inspiring projects and activities, thoughtful, critical and (arguably) examples of organic public geographies, what then is academia’s role

GMRT Discovery of A Millisecond Pulsar in a Very Eccentric Binary System

We report the discovery of the binary millisecond pulsar J0514-4002A, which is the first known pulsar in the globular cluster NGC 1851 and the first pulsar discovered using the Giant Metrewave Radio Telescope (GMRT). The pulsar has a rotational period of 4.99 ms, an orbital period of 18.8 days, and the most eccentric pulsar orbit yet measured (e = 0.89). The companion has a minimum mass of 0.9 M_sun and its nature is presently unclear. After accreting matter from a low-mass companion star which spun it up to a (few) millisecond spin period, the pulsar eventually exchanged the low-mass star for its more massive present companion. This is exactly the same process that could form a system containing a millisecond pulsar and a black hole; the discovery of NGC 1851A demonstrates that such systems might exist in the Universe, provided that stellar mass black holes exist in globular clusters.Comment: 12 pages (referee format), 3 figures, accepted for publication in Astrophysical Journal Letter