5,032 research outputs found
Mirror Symmetry for Calabi-Yau Hypersurfaces in Weighted P_4 and Extensions of Landau Ginzburg Theory
Recently two groups have listed all sets of weights (k_1,...,k_5) such that
the weighted projective space P_4^{(k_1,...,k_5)} admits a transverse
Calabi-Yau hypersurface. It was noticed that the corresponding Calabi-Yau
manifolds do not form a mirror symmetric set since some 850 of the 7555
manifolds have Hodge numbers (b_{11},b_{21}) whose mirrors do not occur in the
list. By means of Batyrev's construction we have checked that each of the 7555
manifolds does indeed have a mirror. The `missing mirrors' are constructed as
hypersurfaces in toric varieties. We show that many of these manifolds may be
interpreted as non-transverse hypersurfaces in weighted P_4's, ie,
hypersurfaces for which dp vanishes at a point other than the origin. This
falls outside the usual range of Landau--Ginzburg theory. Nevertheless
Batyrev's procedure provides a way of making sense of these theories.Comment: 29 pages, plain TeX. Two figures submitted separately as a uuencoded
file. A plot at the end of the paper requires an extended memory version of
TeX. Instructions for suppressing the plot included at head of source fil
Do we need to rethink guidance on repeated interviews?
Within the legal system, children are frequently interviewed about their experiences more than once, with different information elicited in different interviews. The presumed positive and negative effects of multiple interviewing have generated debate and controversy within the legal system and among researchers. Some commentators emphasise that repeated interviews foster inaccurate recall and are inherently suggestive, whereas others emphasise the benefits of allowing witnesses more than one opportunity to recall information. In this article we briefly review the literature on repeated interviewing before presenting a series of cases highlighting what happens when children are interviewed more than once for various reasons. We conclude that, when interviewers follow internationally recognised best-practice guidelines emphasising open-questions and free memory recall, alleged victims of abuse should be interviewed more than once to ensure that more complete accounts are obtained. Implications for current legal guidelines concerning repeated interviewing are discussed
Vacuum field energy and spontaneous emission in anomalously dispersive cavities
Anomalously dispersive cavities, particularly white light cavities, may have
larger bandwidth to finesse ratios than their normally dispersive counterparts.
Partly for this reason, their use has been proposed for use in LIGO-like
gravity wave detectors and in ring-laser gyroscopes. In this paper we analyze
the quantum noise associated with anomalously dispersive cavity modes. The
vacuum field energy associated with a particular cavity mode is proportional to
the cavity-averaged group velocity of that mode. For anomalously dispersive
cavities with group index values between 1 and 0, this means that the total
vacuum field energy associated with a particular cavity mode must exceed . For white light cavities in particular, the group index approaches
zero and the vacuum field energy of a particular spatial mode may be
significantly enhanced. We predict enhanced spontaneous emission rates into
anomalously dispersive cavity modes and broadened laser linewidths when the
linewidth of intracavity emitters is broader than the cavity linewidth.Comment: 9 pages, 4 figure
High resolution radio study of the Pulsar Wind Nebula within the Supernova Remnant G0.9+0.1
We have conducted a radio study at 3.6, 6 and 20 cm using ATCA and VLA and
reprocessed XMM-Newton and Chandra data of the pulsar wind nebula (PWN) in the
supernova remnant (SNR) G0.9+0.1. The new observations revealed that the
morphology and symmetry suggested by Chandra observations (torus and jet-like
features) are basically preserved in the radio range in spite of the rich
structure observed in the radio emission of this PWN, including several arcs,
bright knots, extensions and filaments. The reprocessed X-ray images show for
the first time that the X-ray plasma fills almost the same volume as the radio
PWN. Notably the X-ray maximum does not coincide with the radio maximum and the
neutron star candidate CXOU J174722.8-280915 lies within a small depression in
the radio emission. From the new radio data we have refined the flux density
estimates, obtaining S(PWN) ~ 1.57 Jy, almost constant between 3.6 and 20 cm.
For the whole SNR (compact core and shell), a flux density S(at 20 cm)= 11.5 Jy
was estimated. Based on the new and the existing 90 cm flux density estimates,
we derived alpha(PWN)=-0.18+/-0.04 and alpha(shell)=-0.68+/- 0.07. From the
combination of the radio data with X-ray data, a spectral break is found near
nu ~ 2.4 x 10^(12) Hz. The total radio PWN luminosity is L(radio)=1.2 x 10^(35)
erg s^(-1) when a distance of 8.5 kpc is adopted. By assuming equipartition
between particle and magnetic energies, we estimate a nebular magnetic field B
= 56 muG. The associated particle energy turns out to be U(part)=5 x 10^(47)
erg and the magnetic energy U(mag)=2 x 10^(47) erg. Based on an empirical
relation between X-ray luminosity and pulsar energy loss rate, and the
comparison with the calculated total energy, a lower limit of 1100 yr is
derived for the age of this PWN.Comment: 10 pages,8 figures, accepted for publication in A&A, June 13 200
ANIS: High Energy Neutrino Generator for Neutrino Telescopes
We present the high-energy neutrino Monte Carlo event generator ANIS (All
Neutrino Interaction Simulation). The program provides a detailed and flexible
neutrino event simulation for high-energy neutrino detectors, such as AMANDA,
ANTARES or ICECUBE. It generates neutrinos of any flavor according to a
specified flux and propagates them through the Earth. In a final step neutrino
interactions are simulated within a specified volume. All relevant standard
model processes are implemented. We discuss strengths and limitations of the
program.Comment: 15 pages, 4 figure
Recommended from our members
Complementary Metagenomic Approaches Improve Reconstruction of Microbial Diversity in a Forest Soil.
Soil ecosystems harbor diverse microorganisms and yet remain only partially characterized as neither single-cell sequencing nor whole-community sequencing offers a complete picture of these complex communities. Thus, the genetic and metabolic potential of this "uncultivated majority" remains underexplored. To address these challenges, we applied a pooled-cell-sorting-based mini-metagenomics approach and compared the results to bulk metagenomics. Informatic binning of these data produced 200 mini-metagenome assembled genomes (sorted-MAGs) and 29 bulk metagenome assembled genomes (MAGs). The sorted and bulk MAGs increased the known phylogenetic diversity of soil taxa by 7.2% with respect to the Joint Genome Institute IMG/M database and showed clade-specific sequence recruitment patterns across diverse terrestrial soil metagenomes. Additionally, sorted-MAGs expanded the rare biosphere not captured through MAGs from bulk sequences, exemplified through phylogenetic and functional analyses of members of the phylum Bacteroidetes Analysis of 67 Bacteroidetes sorted-MAGs showed conserved patterns of carbon metabolism across four clades. These results indicate that mini-metagenomics enables genome-resolved investigation of predicted metabolism and demonstrates the utility of combining metagenomics methods to tap into the diversity of heterogeneous microbial assemblages.IMPORTANCE Microbial ecologists have historically used cultivation-based approaches as well as amplicon sequencing and shotgun metagenomics to characterize microbial diversity in soil. However, challenges persist in the study of microbial diversity, including the recalcitrance of the majority of microorganisms to laboratory cultivation and limited sequence assembly from highly complex samples. The uncultivated majority thus remains a reservoir of untapped genetic diversity. To address some of the challenges associated with bulk metagenomics as well as low throughput of single-cell genomics, we applied flow cytometry-enabled mini-metagenomics to capture expanded microbial diversity from forest soil and compare it to soil bulk metagenomics. Our resulting data from this pooled-cell sorting approach combined with bulk metagenomics revealed increased phylogenetic diversity through novel soil taxa and rare biosphere members. In-depth analysis of genomes within the highly represented Bacteroidetes phylum provided insights into conserved and clade-specific patterns of carbon metabolism
Matrices commuting with a given normal tropical matrix
Consider the space of square normal matrices over
, i.e., and .
Endow with the tropical sum and multiplication .
Fix a real matrix and consider the set of matrices
in which commute with . We prove that is a finite
union of alcoved polytopes; in particular, is a finite union of
convex sets. The set of such that is
also a finite union of alcoved polytopes. The same is true for the set
of such that .
A topology is given to . Then, the set is a
neighborhood of the identity matrix . If is strictly normal, then
is a neighborhood of the zero matrix. In one case, is
a neighborhood of . We give an upper bound for the dimension of
. We explore the relationship between the polyhedral complexes
, and , when and commute. Two matrices,
denoted and , arise from , in connection with
. The geometric meaning of them is given in detail, for one example.
We produce examples of matrices which commute, in any dimension.Comment: Journal versio
Engineering—an introduction to a creative profession, G. C. Beakley and H. W. Leach, MaCmillan Company, New York (1968). 548 pages
No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37351/1/690150304_ftp.pd
Introduction to engineering design, Thomas T. Woodson, Mcgraw-Hill, New York (1966). 434 pages, $9.95
No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37349/1/690130502_ftp.pd
History of chemical engineering, William F. Furter, editor, advances in chemistry, series 190, American Chemical Society, Washington, D.C. (1980) 435 pages, $39.00.
No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37386/1/690290229_ftp.pd
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