3,700 research outputs found
Coherent states and the quantization of 1+1-dimensional Yang-Mills theory
This paper discusses the canonical quantization of 1+1-dimensional Yang-Mills
theory on a spacetime cylinder, from the point of view of coherent states, or
equivalently, the Segal-Bargmann transform. Before gauge symmetry is imposed,
the coherent states are simply ordinary coherent states labeled by points in an
infinite-dimensional linear phase space. Gauge symmetry is imposed by
projecting the original coherent states onto the gauge-invariant subspace,
using a suitable regularization procedure. We obtain in this way a new family
of "reduced" coherent states labeled by points in the reduced phase space,
which in this case is simply the cotangent bundle of the structure group K.
The main result explained here, obtained originally in a joint work of the
author with B. Driver, is this: The reduced coherent states are precisely those
associated to the generalized Segal-Bargmann transform for K, as introduced by
the author from a different point of view. This result agrees with that of K.
Wren, who uses a different method of implementing the gauge symmetry. The
coherent states also provide a rigorous way of making sense out of the quantum
Hamiltonian for the unreduced system.
Various related issues are discussed, including the complex structure on the
reduced phase space and the question of whether quantization commutes with
reduction
Anomalous Hall Effect in three ferromagnets: EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30
The Hall resistivity (Rho_xy), resistivity (Rho_xx), and magnetization of
three metallic ferromagnets are investigated as a function of magnetic field
and temperature. The three ferromagnets, EuFe4Sb12 (Tc = 84 K), Yb14MnSb11 (Tc
= 53 K), and Eu8Ga16Ge30 (Tc = 36 K) are Zintl compounds with carrier
concentrations between 1 x 10^21 cm^-3 and 3.5 x 10^21 cm^-3. The relative
decrease in Rho_xx below Tc [Rho_xx(Tc)/Rho_xx(2 K)] is 28, 6.5, and 1.3 for
EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30 respectively. The low carrier
concentrations coupled with low magnetic anisotropies allow a relatively clean
separation between the anomalous (Rho_'xy), and normal contributions to the
measured Hall resistivity. For each compound the anomalous contribution in the
zero field limit is fit to alpha Rho_xx + sigma_xy rho_xx^2 for temperatures T
< Tc. The anomalous Hall conductivity, sigma_xy, is -220 +- 5 (Ohm^-1 cm^-1),
-14.7 +- 1 (Ohm^-1 cm^-1), and 28 +- 3 (Ohm^-1 cm^-1) for EuFe4Sb12,
Yb14MnSb11, and Eu8Ga16Ge30 respectively and is independent of temperature for
T < Tc if the change in spontaneous magnetization (order parameter) with
temperature is taken into account. These data are consistent with recent
theories of the anomalous Hall effect that suggest that even for stochiometric
ferromagnetic crystals, such as those studied in this article, the intrinsic
Hall conductivity is finite at T = 0, and is a ground state property that can
be calculated from the electronic structure.Comment: 22 pages, 13 figures Submitted to PR
Landscape Predictions for the Higgs Boson and Top Quark Masses
If the Standard Model is valid up to scales near the Planck mass, and if the
cosmological constant and Higgs mass parameters scan on a landscape of vacua,
it is well known that the observed orders of magnitude of these quantities can
be understood from environmental selection for large-scale structure and atoms.
If in addition the Higgs quartic coupling scans, with a probability
distribution peaked at low values, environmental selection for a phase having a
scale of electroweak symmetry breaking much less than the Planck scale leads to
a most probable Higgs mass of 106 GeV. While fluctuations below this are
negligible, the upward fluctuation is 25/p GeV, where p measures the strength
of the peaking of the a priori distribution of the quartic coupling. If the top
Yukawa coupling also scans, the most probable top quark mass is predicted to
lie in the range (174--178) GeV, providing the standard model is valid to at
least 10^{17} GeV. The downward fluctuation is 35 GeV/ \sqrt{p}, suggesting
that p is sufficiently large to give a very precise Higgs mass prediction.
While a high reheat temperature after inflation could raise the most probable
value of the Higgs mass to 118 GeV, maintaining the successful top prediction
suggests that reheating is limited to about 10^8 GeV, and that the most
probable value of the Higgs mass remains at 106 GeV. If all Yukawa couplings
scan, then the e,u,d and t masses are understood to be outliers having extreme
values induced by the pressures of strong environmental selection, while the s,
\mu, c, b, \tau Yukawa couplings span only two orders of magnitude, reflecting
an a priori distribution peaked around 10^{-3}. Extensions of these ideas allow
order of magnitude predictions for neutrino masses, the baryon asymmetry and
important parameters of cosmological inflation.Comment: 41 pages; v4: threshold corrrections for top Yukawa are correcte
Military Voting and the Law: Procedural and Technological Solutions to the Ballot Transit Problem
During the 2000 presidential election controversy in Florida, the ballots submitted by individuals living overseasâespecially military votersâwere seen as crucial to the election outcome as the margin of potential victory was so small that these ballots could turn the election from one candidate to the other. Headlines at the time noted that âOdds Against Gore Absentee Gains: Republican-Leaning Counties Appear to Have More Uncounted Overseas Ballots,â âBush Lead Swells with Overseas Votes,â âMilitary Ballot Review is Urged,â and âHow Bush Took Florida: Mining the Overseas Absentee Vote.â For many Americans, however, the controversy surrounding the votes of military personnel and overseas voters, despite its importance, may have seemed both bewildering and esoteric. The debate centered on minute details; whether or not certain overseas absentee ballots were valid and could therefore be counted if they lacked postmarks, were received within given time periods, had missing signature or were deficient in other statutorily required characteristics, that are beyond the interest of the typical individual. However, several key legal skirmishes were fought within the broader context of the recount battle concerning whether certain absentee ballots could be counted, the resolution of which could have swayed the outcome of the 2000 presidential election. Issues of equal protection, federalism and statutory interpretation played large roles in this litigation. The tension between allowing overseas votes to be counted and ensuring a fair election that complied with state law was at the heart of the debate and related litigation
Explaining the Frequency of Alcohol Consumption in a Conflict Zone: Jews and Palestinians in Israel
Experiencing stress and exposure to terrorism may have an adverse effect on health risk behaviors. Few studies have examined alcohol use among adults living in Israel under chronic, stressful terrorism-related conditions. In this study, we examined the relationships of demographics, past stressful events, and terrorism exposure to the frequency of alcohol use and the mediating roles of depressive and post-traumatic stress disorder (PTSD) symptoms. We used three waves of data from a 2007â2008 nationally representative sample of Jewish and Palestinian adults in Israel. We assessed past stressful events, in addition to direct and indirect exposures to terrorism. Results indicated that past stressful events and exposure to terrorism were not directly associated with alcohol use, but were indirectly associated and mediated by depressive and PTSD symptomology. Mental health symptoms were differentially associated with alcohol use. More frequent drinking was mediated by higher levels of depression, including for women and Palestinians; however, PTSD symptom severity was related to less frequent drinking. Mental health may play a prominent role in the frequency of alcohol use among adults exposed to terrorism in Israel. Alcohol use, as a coping mechanism, may differ by demographic characteristics (gender and ethnicity) and psychological symptomology for adults living in a conflict zone in Israel
Coherent states for compact Lie groups and their large-N limits
The first two parts of this article surveys results related to the
heat-kernel coherent states for a compact Lie group K. I begin by reviewing the
definition of the coherent states, their resolution of the identity, and the
associated Segal-Bargmann transform. I then describe related results including
connections to geometric quantization and (1+1)-dimensional Yang--Mills theory,
the associated coherent states on spheres, and applications to quantum gravity.
The third part of this article summarizes recent work of mine with Driver and
Kemp on the large-N limit of the Segal--Bargmann transform for the unitary
group U(N). A key result is the identification of the leading-order large-N
behavior of the Laplacian on "trace polynomials."Comment: Submitted to the proceeding of the CIRM conference, "Coherent states
and their applications: A contemporary panorama.
Density Perturbations and the Cosmological Constant from Inflationary Landscapes
An anthropic understanding of the cosmological constant requires that the
vacuum energy at late time scans from one patch of the universe to another. If
the vacuum energy during inflation also scans, the various patches of the
universe acquire exponentially differing volumes. In a generic landscape with
slow-roll inflation, we find that this gives a steeply varying probability
distribution for the normalization of the primordial density perturbations,
resulting in an exponentially small fraction of observers measuring the COBE
value of 10^-5. Inflationary landscapes should avoid this "\sigma problem", and
we explore features that can allow them to do that. One possibility is that,
prior to slow-roll inflation, the probability distribution for vacua is
extremely sharply peaked, selecting essentially a single anthropically allowed
vacuum. Such a selection could occur in theories of eternal inflation. A second
possibility is that the inflationary landscape has a special property: although
scanning leads to patches with volumes that differ exponentially, the value of
the density perturbation does not vary under this scanning. This second case is
preferred over the first, partly because a flat inflaton potential can result
from anthropic selection, and partly because the anthropic selection of a small
cosmological constant is more successful.Comment: 23 page
Cells exhibiting strong p16INK4a promoter activation in vivo display features of senescence
The activation of cellular senescence throughout the lifespan promotes tumor suppression, whereas the persistence of senescent cells contributes to aspects of aging. This theory has been limited, however, by an inability to identify and isolate individual senescent cells within an intact organism. Toward that end, we generated a murine reporter strain by âknocking-inâ a fluorochrome, tandem-dimer Tomato (tdTom), into exon 1α of the p16 INK4a locus. We used this allele (p16 tdTom ) for the enumeration, isolation, and characterization of individual p16 INK4a -expressing cells (tdTom + ). The half-life of the knocked-in transcript was shorter than that of the endogenous p16 INK4a mRNA, and therefore reporter expression better correlated with p16 INK4a promoter activation than p16 INK4a transcript abundance. The frequency of tdTom + cells increased with serial passage in cultured murine embryo fibroblasts from p16 tdTom/+ mice. In adult mice, tdTom + cells could be readily detected at low frequency in many tissues, and the frequency of these cells increased with aging. Using an in vivo model of peritoneal inflammation, we compared the phenotype of cells with or without activation of p16 INK4a and found that tdTom + macrophages exhibited some features of senescence, including reduced proliferation, senescence-associated ÎČ-galactosidase (SA-ÎČ-gal) activation, and increased mRNA expression of a subset of transcripts encoding factors involved in SA-secretory phenotype (SASP). These results indicate that cells harboring activation of the p16 INK4a promoter accumulate with aging and inflammation in vivo, and display characteristics of senescence
Management of the Brown-Headed Cowbird: Implications for Endangered Species and Agricultural Damage Mitigation
The brown-headed cowbird (Molothrus ater; cowbird) is unique among North American blackbirds (Icteridae) because it is managed to mitigate the negative effects on endangered songbirds and economic losses in agricultural crops. Cowbird brood parasitism can further affect species that are considered threatened or endangered due to anthropogenic land uses. Historically, cowbirds have often been culled without addressing ultimate causes of songbird population declines. Similar to other North American blackbirds, cowbirds depredate agricultural crops, albeit at a lower rate reported for other blackbird species. Conflicting information exists on the extent of agricultural damage caused by cowbirds and the effectiveness of mitigation measures for application to management. In this paper, we reviewed the progress that has been made in cowbird management from approximately 2005 to 2020 in relation to endangered species. We also reviewed losses to the rice (Oryza sativa) crop attributed to cowbirds and the programs designed to reduce depredation. Of the 4 songbird species in which cowbirds have been managed, both the Kirtlandâs warbler (Dendroica kirtlandii) and black-capped vireo (Vireo atricapilla) have been removed from the endangered species list following population increases in response to habitat expansion. Cowbird trapping has ceased for Kirtlandâs warbler but continues for the vireo. In contrast, least Bellâs vireo (V. bellii pusillus) and southwestern willow flycatcher (Empidonax traillii extimus) still require cowbird control after modest increases in suitable habitat. Our review of rice depredation by cowbirds revealed models that have been created to determine the number of cowbirds that can be taken to decrease rice loss have been useful but require refinement with new data that incorporate cowbird population changes in the rice growing region, dietary preference studies, and current information on population sex ratios and female cowbird egg laying. Once this information has been gathered, bioenergetic and economic models would increase our understanding of the damage caused by cowbirds
Longâterm hematologic and clinical outcomes of splenectomy in children with hereditary spherocytosis and sickle cell disease
BackgroundTotal splenectomy (TS) and partial splenectomy (PS) are used for children with congenital hemolytic anemia (CHA), although the longâterm outcomes of these procedures are poorly defined. This report describes longâterm outcomes of children with CHA requiring TS or PS.ProcedureWe collected data from children ages 2â17 with hereditary spherocytosis (HS) or sickle cell disease (SCD) requiring TS or PS from 1996 to 2016 from 14 sites in the Splenectomy in Congenital Hemolytic Anemia (SICHA) consortium using a prospective, observational patient registry. We summarized hematologic outcomes, clinical outcomes, and adverse events to 5 years after surgery. Hematologic outcomes were compared using mixed effects modeling.ResultsOver the study period, 110 children with HS and 97 children with SCD underwent TS or PS. From preoperatively compared to postoperatively, children with HS increased their mean hemoglobin level by 3.4Â g/dL, decreased their mean reticulocyte percentage by 6.7%, and decreased their mean bilirubin by 2.4Â mg/dL. Hematologic improvements and improved clinical outcomes were sustained over 5 years of followâup. For children with SCD, there was no change in hemoglobin after PS or TS following surgery, although all clinical outcomes were improved. Over 5 years, there was one child with HS and five children with SCD who developed postsplenectomy sepsis.ConclusionsFor children with HS, there are excellent longâterm hematologic and clinical outcomes following either PS or TS. Although hemoglobin levels do not change after TS or PS in SCD, the longâterm clinical outcomes for children with SCD are favorable.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155920/1/pbc28290.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155920/2/pbc28290_am.pd
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