Quasi-stationary regime of a branching random walk in presence of an absorbing wall

A branching random walk in presence of an absorbing wall moving at a constant velocity $v$ undergoes a phase transition as the velocity $v$ of the wall varies. Below the critical velocity $v_c$, the population has a non-zero survival probability and when the population survives its size grows exponentially. We investigate the histories of the population conditioned on having a single survivor at some final time $T$. We study the quasi-stationary regime for $v<v_c$ when $T$ is large. To do so, one can construct a modified stochastic process which is equivalent to the original process conditioned on having a single survivor at final time $T$. We then use this construction to show that the properties of the quasi-stationary regime are universal when $v\to v_c$. We also solve exactly a simple version of the problem, the exponential model, for which the study of the quasi-stationary regime can be reduced to the analysis of a single one-dimensional map.Comment: 2 figures, minor corrections, one reference adde

Noncommutative Topological Theories of Gravity

The possibility of noncommutative topological gravity arising in the same manner as Yang-Mills theory is explored. We use the Seiberg-Witten map to construct such a theory based on a SL(2,C) complex connection, from which the Euler characteristic and the signature invariant are obtained. This gives us a way towards the description of noncommutative gravitational instantons as well as noncommutative local gravitational anomalies.Comment: 17+1 pages, LaTeX, no figures, some clarifications, comments and references added, style improve

IMPACT: The Journal of the Center for Interdisciplinary Teaching and Learning. Volume 10, Issue 1, Winter 2021

In this issue, a central question explored is, what kinds of programs and approaches can enhance interdisciplinary teaching and student learning? The essays in this issue explore this question in distinct and insightful ways. Grounded in her own experiences developing and running a Latin American and Caribbean Studies minor, one contributor argues that the minor enhances students’ interdisciplinary learning by exposing students to ethnic and racial difference, enriches student understanding of the depth and breadth of geo-cultural diversity, and prepares students to engage and work in multicultural settings. Writing together, two health educators highlight how various applications of service-learning pedagogy, such as traditional vs. online classroom approaches to service learning, application of service-learning strategies in the context of health education and health promotion, via internship courses and funded service projects, and the role of service-learning in enhancing core areas of responsibilities for certified health education specialists (CHES), can be a powerful interdisciplinary teaching and learning tool in health education. Finally, two faculty from the University of Tennessee interested in the Biglan/Becher taxonomy of disciplines, collaboratively show how the Biglan/Becher taxonomy of disciplines can be used to analyze disciplinary interrelationships in STEAM (STEM + Arts), with the ultimate goal of categorizing ways STEAM approaches can facilitate student learning in higher education. Our Impact book reviewers inform readers about new interdisciplinary and ground-breaking work in the under-researched area of parental incarceration, one author’s suggestions for how to teach undergraduates and still feel good about it, notes from a white professor in terms of teaching about race and racism in the college classroom, and, finally, another author’s arguments about how democracy can handle climate change

Equivalence of 2 effective graft-versus-host disease prophylaxis regimens: Results of a prospective double-blind randomized trial

AbstractWe have previously demonstrated a decrease in the incidence of acute graft-versus-host disease (GVHD) with the addition of methotrexate (MTX) to cyclosporine (CSP) and prednisone (PSE) chemotherapy in patients with leukemia. We have now completed a prospective randomized trial comparing the 3-drug regimen (CSP/MTX/PSE, including 3 doses of MTX) to the standard 2-drug regimen (CSP/MTX, including 4 doses of MTX) to investigate the benefit of PSE used up front for the prevention of acute and chronic GVHD. In the trial, 193 patients were randomized and 186 were included in the final analysis. All patients received a bone marrow graft from a fully histocompatible sibling donor. The preparatory regimen consisted of fractionated total-body irradiation (fTBI) and etoposide in all but 13 patients, who received fTBI and cyclophosphamide. The patients were randomized to receive either CSP/MTX/PSE or CSP/MTX. The 2 groups were well balanced with respect to diagnosis, disease stage, age, donor-recipient sex, and parity. In an intent-to-treat analysis, the incidence of acute GVHD was 18% (95% confidence interval [CI] 12-28) for the CSP/MTX/PSE group compared with 20% (CI 10-26) for the CSP/,MTX group (P = .60), with a median follow up of 2.2 years. Overall survival was 65% for those receiving CSP/MTX/PSE and 72% for those receiving CSP/MTX (P = .10); the relapse rate was 15% for the CSP/MTX/PSE group and 12% for the CSP/MTX group (P = .83). The incidence of chronic GVHD was similar (46% versus 52%; P = .38), with a follow-up of 0.7 to 6.0 years. Of interest, 21 patients went off study due to GVHD (5 in the CSP/MTX/PSE group and 16 in the CSP/MITX group [P = .02]), and 11 patients went off study because of alveolar hemorrhage (3 in the CSP/MTX/PSE group and 8 in the CSP/MTX group [P = .22]). The addition of PSE did not result in a higher incidence of infectious complications, bacterial (66% versus 58%), viral (77% versus 66%), or fungal (20% versus 20%), in those receiving CSP/MTX/PSE versus CSP/MTX, respectively. These data suggest that the addition of PSE was associated with a somewhat lower incidence of early posttransplantation complications but did not have a positive impact on the incidence of acute or chronic GVHD or event-free or overall survival.Biol Blood Marrow Transplant 2000;6(3):254-61

Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models

Both community ecology and conservation biology seek further understanding of factors governing the advance of an invasive species. We model biological invasion as an individual-based, stochastic process on a two-dimensional landscape. An ecologically superior invader and a resident species compete for space preemptively. Our general model includes the basic contact process and a variant of the Eden model as special cases. We employ the concept of a "roughened" front to quantify effects of discreteness and stochasticity on invasion; we emphasize the probability distribution of the front-runner's relative position. That is, we analyze the location of the most advanced invader as the extreme deviation about the front's mean position. We find that a class of models with different assumptions about neighborhood interactions exhibit universal characteristics. That is, key features of the invasion dynamics span a class of models, independently of locally detailed demographic rules. Our results integrate theories of invasive spatial growth and generate novel hypotheses linking habitat or landscape size (length of the invading front) to invasion velocity, and to the relative position of the most advanced invader.Comment: The original publication is available at www.springerlink.com/content/8528v8563r7u2742

From thermal rectifiers to thermoelectric devices

We discuss thermal rectification and thermoelectric energy conversion from the perspective of nonequilibrium statistical mechanics and dynamical systems theory. After preliminary considerations on the dynamical foundations of the phenomenological Fourier law in classical and quantum mechanics, we illustrate ways to control the phononic heat flow and design thermal diodes. Finally, we consider the coupled transport of heat and charge and discuss several general mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays

Average charged multiplicities have been measured separately in $b$, $c$ and light quark ($u,d,s$) events from $Z^0$ decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of $b$ and light quark events, and reconstructed charmed mesons were used to select $c$ quark events. We measured the charged multiplicities: $\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.})$, $\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ^{+0.41}_{-0.36}(\rm{syst.})$ $\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ^{+0.38}_{-0.37}(\rm{syst.})$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})^{+0.36}_{-0.30}(\rm{syst.})$ and $\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})^{+0.30}_{-0.29}(\rm{syst.})$. We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters

The solution to the Tullock rent-seeking game when R > 2: mixed-strategy equilibria and mean dissipation rates

In Tullock's rent-seeking model, the probability a player wins the game depends on expenditures raised to the power R. We show that a symmetric mixed-strategy Nash equilibrium exists when R>2, and that overdissipation of rents does not arise in any Nash equilibrium. We derive a tight lower bound on the level of rent dissipation that arises in a symmetric equilibrium when the strategy space is discrete, and show that full rent dissipation occurs when the strategy space is continuous. Our results are shown to be consistent with recent experimental evidence on the dissipation of rents. An earlier version of this paper circulated under the title, No, Virginia, There is No Overdissipation of Rents. We are grateful to Dave Furth and Frans van Winden for stimulating conversations, and for comments provided by workshop participants from the CORE-ULB-KUL IUAP project, Purdue University, Pennsylvania State University, Rijksuniversiteit Limburg, and Washington State University. We also thank Max van de Sande Bakhuyzen and Ben Heijdra for useful discussions, and Geert Gielens for computational assistance. An earlier version of the paper was presented at the ESEM 1992 in Brussels and the Mid-West Mathematical Economics Conference in Pittsburgh. All three authors would like to thank CentER for its hospitality during the formative stages of the paper. The second author has also benefited from the financial support of the Katholieke Universitieit Leuven and the Jay N. Ross Young Faculty Scholar Award at Purdue University. The third author benefitted from visiting IGIER where part of the paper was written. The third author also benefitted from grant IUAP 26 of the Belgian Government

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results