Complex Matrix Models and Statistics of Branched Coverings of 2D Surfaces

We present a complex matrix gauge model defined on an arbitrary two-dimensional orientable lattice. We rewrite the model's partition function in terms of a sum over representations of the group U(N). The model solves the general combinatorial problem of counting branched covers of orientable Riemann surfaces with any given, fixed branch point structure. We then define an appropriate continuum limit allowing the branch points to freely float over the surface. The simplest such limit reproduces two-dimensional chiral U(N) Yang-Mills theory and its string description due to Gross and Taylor.Comment: 21 pages, 2 figures, TeX, harvmac.tex, epsf.tex, TeX "big

The Future of Physicians’ First Amendment Freedom: Professional Speech in an Era of Radically Expanded Prenatal Genetic Testing

This Article explores the First Amendment questions prenatal whole genome sequencing (PWGS) is likely to raise. It argues that most of the foreseeable options for state intervention in conversations between physicians and prospective parents about genetic sequencing should trigger at least heightened scrutiny. Part I provides an overview of the most recent advances in genetic testing. It assesses the ongoing impact of non-invasive prenatal testing (NIPT) for providers and patients and charts the course from NIPT to PWGS. Part II establishes a foundational background for evaluating First Amendment claims. Part II.A describes the development of First Amendment jurisprudence, focusing on the doctrinal distinctions between levels of judicial scrutiny. Part II.B explores historical Supreme Court case law addressing professional speech. Part III surveys the current legal landscape. Using a handful of recent Circuit cases, Part III.A demonstrates that the legal frameworks for assessing physician speech qua professional speech are shambolic. Part III.B provides an overview of the most recent Supreme Court ruling on professional speech in the 2018 case National Institute of Family and Life Advocates v. Becerra. Part IV uses the material in Parts I–III to predict how legislative efforts to limit reproductive decision-making are likely to manifest in the PWGS context. Based on the case analyses in Part III, Part IV identifies the Fourth and Eleventh Circuit approaches as the most defensible for future judicial interventions. This Article concludes that state-based restrictions on PWGS-related speech would be vulnerable to First Amendment challenges and unlikely to survive heightened judicial scrutiny

Matrix String Partition Functions

We evaluate quasi-classically the Ramond partition function of Euclidean D=10 U(N) super-Yang--Mills theory reduced to a two-dimensional torus. The result can be interpreted in terms of free strings wrapping the space-time torus, as expected from the point of view of Matrix string theory. We demonstrate that, when extrapolated to the ultraviolet limit (small area of the torus), the quasi-classical expressions reproduce exactly the recently obtained expression for the partition of the completely reduced SYM theory, including the overall numerical factor. This is an evidence that our quasi-classical calculation might be exact.Comment: harvmac (b), 15 pages. v2 Cosmetic changes in the text and references adde

COVID-19 vaccination perceptions and intentions of maternity care consumers and providers in Australia.

IntroductionVaccination against COVID-19 is a key global public health strategy. Health professionals including midwives and doctors support and influence vaccination uptake by childbearing women. There is currently no evidence regarding the COVID-19 vaccination perceptions and intentions of those who receive or provide maternity care in Australia. The aim of this study was to address this gap in knowledge and explore the perceptions and intentions regarding COVID-19 vaccination from consumers and providers of maternity care in Australia.MethodsA national cross-sectional online study conducted in early 2021 in Australia, a country that has had a very low number of COVID-19 cases and deaths. Recruitment was undertaken through parenting and health professional social media sites and professional college distribution lists. A total of 853 completed responses, from women (n = 326), maternity care providers including doctors (n = 58), midwives (n = 391) and midwifery students (n = 78).FindingsPersonal intention to be vaccinated ranged from 48-89% with doctors most likely and women least likely. Doctors and midwifery students were significantly more likely to recommend the vaccine to pregnant women in their care than midwives (pConclusionThis is the first study to explore the perceptions and intentions regarding COVID-19 vaccination from the perspective of those who receive and provide maternity care in Australia. Findings have utility to support targeted public health messaging for these and other cohorts

Experiences of receiving and providing maternity care during the COVID-19 pandemic in Australia: A five-cohort cross-sectional comparison.

Introduction The global COVID-19 pandemic has radically changed the way health care is delivered in many countries around the world. Evidence on the experience of those receiving or providing maternity care is important to guide practice through this challenging time. Methods A cross-sectional study was conducted in Australia. Five key stakeholder cohorts were included to explore and compare the experiences of those receiving or providing care during the COVID-19 pandemic. Women, their partners, midwives, medical practitioners and midwifery students who had received or provided maternity care from March 2020 onwards in Australia were recruited via social media and invited to participate in an online survey released between 13th May and 24th June 2020; a total of 3701 completed responses were received. Findings While anxiety related to COVID-19 was high among all five cohorts, there were statistically significant differences between the responses from each cohort for most survey items. Women were more likely to indicate concern about their own and family’s health and safety in relation to COVID-19 whereas midwives, doctors and midwifery students were more likely to be concerned about occupational exposure to COVID-19 through working in a health setting than those receiving care through attending these environments. Midwifery students and women’s partners were more likely to respond that they felt isolated because of the changes to the way care was provided. Despite concerns about care received or provided not meeting expectations, most respondents were satisfied with the quality of care provided, although midwives and midwifery students were less likely to agree. Conclusion This paper provides a unique exploration and comparison of experiences of receiving and providing maternity care during the COVID-19 pandemic in Australia. Findings are useful to support further service changes and future service redesign. New evidence provided offers unique insight into key stakeholders’ experiences of the rapid changes to health services

Matrix Theory Interpretation of DLCQ String Worldsheets

We study the null compactification of type-IIA-string perturbation theory at finite temperature. We prove a theorem about Riemann surfaces establishing that the moduli spaces of infinite-momentum-frame superstring worldsheets are identical to those of branched-cover instantons in the matrix-string model conjectured to describe M-theory. This means that the identification of string degrees of freedom in the matrix model proposed by Dijkgraaf, Verlinde and Verlinde is correct and that its natural generalization produces the moduli space of Riemann surfaces at all orders in the genus expansion.Comment: 9 pages LaTeX. Changes in style, typos correcte

Fuzzy Spheres in pp Wave Matrix String Theory

The behaviour of matrix string theory in the background of a type IIA pp wave at small string coupling, g_s << 1, is determined by the combination M g_s where M is a dimensionless parameter proportional to the strength of the Ramond-Ramond background. For M g_s << 1, the matrix string theory is conventional; only the degrees of freedom in the Cartan subalgebra contribute, and the theory reduces to copies of the perturbative string. For M g_s >> 1, the theory admits degenerate vacua representing fundamental strings blown up into fuzzy spheres with nonzero lightcone momenta. We determine the spectrum of small fluctuations around these vacua. Around such a vacuum all N-squared degrees of freedom are excited with comparable energies. The spectrum of masses has a spacing which is independent of the radius of the fuzzy sphere, in agreement with expected behaviour of continuum giant gravitons. Furthermore, for fuzzy spheres characterized by reducible representations of SU(2) and vanishing Wilson lines, the boundary conditions on the field are characterized by a set of continuous angles which shows that generically the blown up strings do not ``close''.Comment: 45 pages REVTeX 4 and AMSLaTeX. 1 figure. v2: references added. Figure redrawn using LaTe

Feasibility of implementation and the impact of a digital prehabilitation service in patients undergoing treatment for oesophago-gastric cancer

Background: Home-based and supervised prehabilitation programmes are shown to have a positive impact on outcomes in patients with oesophago-gastric (OG) cancer. The primary aim of this study was to establish the feasibility of delivering a digital prehabilitation service. Methods: Patients undergoing treatment for OG cancer with curative intent were recruited into the study. During the COVID-19 pandemic, patients were offered a digital prehabilitation service. Following the lifting of COVID-19 restrictions, patients were also offered both a hybrid clinic-based in-person service and a digital service. Implementation and clinical metrics from the two prehabilitation models were compared. Results: 31 of 41 patients accepted the digital service (75%). Of the people who started the digital programme, 3 dropped out (10%). Compliance with the weekly touchpoints was 86%, and the median length of programme was 12 weeks. Twenty-six patients enrolled in the in-person service. Two patients dropped out (10%). Average compliance to weekly touchpoints was 71%, and the median length of programme was 10 weeks. In the digital group, sit to stand (STS) increased from 14.5 (IQR 10.5–15.5) to 16 (IQR 16–22); p = 0.02. Median heart rate recovery (HRR) increased from 10.5 (IQR 7.5–14) to 15.5 (IQR 11–20) bpm; p = 0.24. There was a significant drop in distress (median 3 (IQR 0–5) to 1 (IQR 0–2); p = 0.04) and a small drop in anxiety (median 3 (0–5) to 2 (0–3); p = 0.22). There was no difference in the postoperative complication rate and length of hospital stay between the two groups. Discussion: This study has shown that digital prehabilitation can be delivered effectively to patients with OG cancer, with high engagement and retention rates. We observed improvements in some physical and psychological parameters with the digital service, with comparable clinical outcomes to the in-person service