2,479 research outputs found
Charge-Focusing Readout of Time Projection Chambers
Time projection chambers (TPCs) have found a wide range of applications in
particle physics, nuclear physics, and homeland security. For TPCs with
high-resolution readout, the readout electronics often dominate the price of
the final detector. We have developed a novel method which could be used to
build large-scale detectors while limiting the necessary readout area. By
focusing the drift charge with static electric fields, we would allow a small
area of electronics to be sensitive to particle detection for a much larger
detector volume. The resulting cost reduction could be important in areas of
research which demand large-scale detectors, including dark matter searches and
detection of special nuclear material. We present simulations made using the
software package Garfield of a focusing structure to be used with a prototype
TPC with pixel readout. This design should enable significant focusing while
retaining directional sensitivity to incoming particles. We also present first
experimental results and compare them with simulation.Comment: 5 pages, 17 figures, Presented at IEEE Nuclear Science Symposium 201
Inflation by non-minimal coupling
Inflationary scenarios based on simple non-minimal coupling and its
generalizations are studied. Generalizing the form of non-minimal coupling to
"K(phi)R" with an arbitrary function K(phi), we show that the flat potential
still is obtainable when V(phi)/K^2(phi) is asymptotically constant. Very
interestingly, if the ratio of the dimensionless self-coupling constant of the
inflaton field and the non-minimal coupling constant is small the cosmological
observables for general monomial cases are in good agreement with recent
observational data.Comment: 9 pages, 1 figur
On bulk singularities in the random normal matrix model
We extend the method of rescaled Ward identities of Ameur-Kang-Makarov to
study the distribution of eigenvalues close to a bulk singularity, i.e. a point
in the interior of the droplet where the density of the classical equilibrium
measure vanishes. We prove results to the effect that a certain "dominant part"
of the Taylor expansion determines the microscopic properties near a bulk
singularity. A description of the distribution is given in terms of a special
entire function, which depends on the nature of the singularity (a
Mittag-Leffler function in the case of a rotationally symmetric singularity).Comment: This version clarifies on the proof of Theorem
Calabi-Yau Orbifolds and Torus Coverings
The theory of coverings of the two-dimensional torus is a standard part of
algebraic topology and has applications in several topics in string theory, for
example, in topological strings. This paper initiates applications of this
theory to the counting of orbifolds of toric Calabi-Yau singularities, with
particular attention to Abelian orbifolds of C^D. By doing so, the work
introduces a novel analytical method for counting Abelian orbifolds, verifying
previous algorithm results. One identifies a p-fold cover of the torus T^{D-1}
with an Abelian orbifold of the form C^D/Z_p, for any dimension D and a prime
number p. The counting problem leads to polynomial equations modulo p for a
given Abelian subgroup of S_D, the group of discrete symmetries of the toric
diagram for C^D. The roots of the polynomial equations correspond to orbifolds
of the form C^D/Z_p, which are invariant under the corresponding subgroup of
S_Ds. In turn, invariance under this subgroup implies a discrete symmetry for
the corresponding quiver gauge theory, as is clearly seen by its brane tiling
formulation.Comment: 33 pages, 5 figures, 7 tables; version published on JHE
Explicit CP violation in the Dine-Seiberg-Thomas model
The possibility of explicit CP violation is studied in a supersymmetric model
proposed by Dine, Seiberg, and Thomas, with two effective dimension-five
operators. The explicit CP violation may be triggered by complex phases in the
coefficients for the dimension-five operators in the Higgs potential, and by a
complex phase in the scalar top quark masses. Although the scenario of explicit
CP violation is found to be inconsistent with the experimental data at LEP2 at
the tree level, it may be possible at the one-loop level. For a reasonable
parameter space, the masses of the neutral Higgs bosons and their couplings to
a pair of bosons are consistent with the LEP2 data, at the one-loop level.Comment: 5 pages, 2 figure
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster (GC) system in the
giant elliptical galaxy (gE) M60 in the Virgo cluster. Using the photometric
and spectroscopic database of 121 GCs (83 blue GCs and 38 red GCs), we have
investigated the kinematics of the GC system. We have found that the M60 GC
system shows a significant overall rotation. The rotation amplitude of the blue
GCs is slightly smaller than or similar to that of the red GCs, and their
angles of rotation axes are similar. The velocity dispersions about the mean
velocity and about the best fit rotation curve for the red GCs are marginally
larger than those for the blue GCs. Comparison of observed stellar and GC
velocity dispersion profiles with those calculated from the stellar mass
profile shows that the mass-to-light ratio should be increased as the
galactocentric distance increases, indicating the existence of an extended dark
matter halo. The entire sample of GCs in M60 is found to have a tangentially
biased velocity ellipsoid unlike the GC systems in other gEs. Two subsamples
appear to have different velocity ellipsoids. The blue GC system has a modest
tangentially biased velocity ellipsoid, while the red GC system has a modest
radially biased or an isotropic velocity ellipsoid. From the comparison of the
kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC
1399, NGC 5128, and NGC 4636), it is found that the velocity dispersion of the
blue GC system is similar to or larger than that of the red GC system except
for M60, and the rotation of the GC system is not negligible. The entire sample
of each GC system shows an isotropic velocity ellipsoid except for M60, while
the subsamples show diverse velocity ellipsoids. We discuss the implication of
these results for the formation models of the GC system in gEs.Comment: 48 pages, 16 figures. To appear in Ap
Exploiting Inter- and Intra-Memory Asymmetries for Data Mapping in Hybrid Tiered-Memories
Modern computing systems are embracing hybrid memory comprising of DRAM and
non-volatile memory (NVM) to combine the best properties of both memory
technologies, achieving low latency, high reliability, and high density. A
prominent characteristic of DRAM-NVM hybrid memory is that it has NVM access
latency much higher than DRAM access latency. We call this inter-memory
asymmetry. We observe that parasitic components on a long bitline are a major
source of high latency in both DRAM and NVM, and a significant factor
contributing to high-voltage operations in NVM, which impact their reliability.
We propose an architectural change, where each long bitline in DRAM and NVM is
split into two segments by an isolation transistor. One segment can be accessed
with lower latency and operating voltage than the other. By introducing tiers,
we enable non-uniform accesses within each memory type (which we call
intra-memory asymmetry), leading to performance and reliability trade-offs in
DRAM-NVM hybrid memory. We extend existing NVM-DRAM OS in three ways. First, we
exploit both inter- and intra-memory asymmetries to allocate and migrate memory
pages between the tiers in DRAM and NVM. Second, we improve the OS's page
allocation decisions by predicting the access intensity of a newly-referenced
memory page in a program and placing it to a matching tier during its initial
allocation. This minimizes page migrations during program execution, lowering
the performance overhead. Third, we propose a solution to migrate pages between
the tiers of the same memory without transferring data over the memory channel,
minimizing channel occupancy and improving performance. Our overall approach,
which we call MNEME, to enable and exploit asymmetries in DRAM-NVM hybrid
tiered memory improves both performance and reliability for both single-core
and multi-programmed workloads.Comment: 15 pages, 29 figures, accepted at ACM SIGPLAN International Symposium
on Memory Managemen
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