2,342 research outputs found
Interaction of vortices in thin superconducting films and Berezinskii-Kosterlitz-Thouless transition
The precondition for the BKT transition in thin superconducting films, the
logarithmic intervortex interaction, is satisfied at distances short relative
to , is the London penetration depth of the
bulk material and is the film thickness. For this reason, the search for
the transition has been conducted in samples of the size . It is
argued below that film edges turn the interaction into near exponential
(short-range) thus making the BKT transition impossible. If however the
substrate is superconducting and separated from the film by an insulated layer,
the logarithmic intervortex interaction is recovered and the BKT transition
should be observable.Comment: 4 pages, no figure
The Moyal bracket and the dispersionless limit of the KP hierarchy
A new Lax equation is introduced for the KP hierarchy which avoids the use of
pseudo-differential operators, as used in the Sato approach. This Lax equation
is closer to that used in the study of the dispersionless KP hierarchy, and is
obtained by replacing the Poisson bracket with the Moyal bracket. The
dispersionless limit, underwhich the Moyal bracket collapses to the Poisson
bracket, is particularly simple.Comment: 9 pages, LaTe
Public understanding and awareness of and response to monkeypox virus outbreak: A cross-sectional survey of the most affected communities in the United Kingdom during the 2022 public health emergency.
OBJECTIVES: Our objective was to examine the public response to public health and media messaging during the human monkeypox virus (MPXV) outbreak in the UK, focusing on at-risk communities. METHODS: A co-produced, cross-sectional survey was administered in June and July 2022 using community social media channels and the Grindr dating app. Basic descriptive statistics, logistic regression, and odds ratio p values are presented. RESULTS: Of 1932 survey respondents, 1750 identified as men, 88 as women, and 64 as gender non-conforming. Sexual identity was described as gay/lesbian/queer (80%), bisexual (12%), heterosexual (4%), and pansexual (2%); 39% were aged <40 years; 71% self-identified as White, 3% as Black, 8% as Asian, 2%as LatinX, and 11% as 'Mixed or Other' heritage groups. In total, 85% were employed and 79% had completed higher education. A total of 7% of respondents identified themselves as living with HIV. Overall, 34% reported limited understanding of public health information, 52% considered themselves at risk, 61% agreed that people with MPXV should isolate for 21 days, 49% reported they would first attend a sexual health clinic if symptomatic, 86% reported they would accept a vaccine, and 59% believed that MPXV originated from animals. The most trusted sources of information were healthcare professionals (37%), official health agencies (29%), and mainstream media (12%). CONCLUSIONS: Vaccine acceptability was very high, yet the understanding and acceptance of public health information varied. Social determinants of health inequalities already shaping the UK landscape risk were compounded in this new emergency. Engagement with structurally disadvantaged members of affected communities and better dissemination of public health messaging by trusted healthcare professionals are essential for the public health response
A broken solar type II radio burst induced by a coronal shock propagating across the streamer boundary
We discuss an intriguing type II radio burst that occurred on 2011 March 27.
The dynamic spectrum was featured by a sudden break at about 43 MHz on the
well-observed harmonic branch. Before the break, the spectrum drifted gradually
with a mean rate of about -0.05 MHz/s. Following the break, the spectrum jumped
to lower frequencies. The post-break emission lasted for about three minutes.
It consisted of an overall slow drift which appeared to have a few fast drift
sub-bands. Simultaneous observations from the Solar TErrestrial RElations
Observatory (STEREO) and the Solar Dynamics Observatory (SDO) were also
available and are examined for this event. We suggest that the slow-drift
period before the break was generated inside a streamer by a coronal eruption
driven shock, and the spectral break as well as the relatively wide spectrum
after the break is a consequence of the shock crossing the streamer boundary
where density drops abruptly. It is suggested that this type of radio bursts
can be taken as a unique diagnostic tool for inferring the coronal density
structure, as well as the radio emitting source region.Comment: 12 pages, 5 figures, accepted by ApJ 201
A Quasiperiodic Gibbons--Hawking Metric and Spacetime Foam
We present a quasiperiodic self-dual metric of the Gibbons--Hawking type with
one gravitational instanton per spacetime cell. The solution, based on an
adaptation of Weierstrassian and functions to three
dimensions, conforms to a definition of spacetime foam given by Hawking.Comment: 14 pages, Late
Re-examining the consumption-wealth relationship : the role of model uncertainty
This paper discusses the consumption-wealth relationship. Following the recent influential workof Lettau and Ludvigson [e.g. Lettau and Ludvigson (2001), (2004)], we use data on consumption, assets andlabor income and a vector error correction framework. Key …ndings of their work are that consumption doesrespond to permanent changes in wealth in the expected manner, but that most changes in wealth are transitoryand have no e¤ect on consumption. We investigate the robustness of these results to model uncertainty andargue for the use of Bayesian model averaging. We …nd that there is model uncertainty with regards to thenumber of cointegrating vectors, the form of deterministic components, lag length and whether the cointegratingresiduals a¤ect consumption and income directly. Whether this uncertainty has important empirical implicationsdepends on the researcher's attitude towards the economic theory used by Lettau and Ludvigson. If we workwith their model, our findings are very similar to theirs. However, if we work with a broader set of models andlet the data speak, we obtain somewhat di¤erent results. In the latter case, we …nd that the exact magnitudeof the role of permanent shocks is hard to estimate precisely. Thus, although some support exists for the viewthat their role is small, we cannot rule out the possibility that they have a substantive role to play
Two-component generalizations of the Camassa-Holm equation
A classification of integrable two-component systems of non-evolutionary partial differential equations that are analogous to the Camassa-Holm equation is carried out via the perturbative symmetry approach. Independently, a classification of compatible pairs of Hamiltonian operators is carried out, which leads to bi-Hamiltonian structures for the same systems of equations. Some exact solutions and Lax pairs are also constructed for the systems considered
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