37,431 research outputs found
The Failure of Local and Federal Prosecutors to Curb Police Brutality
Although police departments across the country have attempted to ameliorate the hostility between police officers and the cumminity, through careful screening of applicants, minority recruitment, and community policing, police brutality remains a problem within our urban cities. This Essay will first argue that police brutality is largely ignored. Second, it will examine the obstacles facing local and federal prosecutors in obtaining convictions. Then it will compare the advantages and disadvantages of delegating primary responsibility for these cases to the state versus the federal level. Finally, it will argue that, although there are obstacles and advantages for both local and federal prosecutors, ultimately justice is best seved when police brutality is primarily pursued by local prosecutors
The Binary Galaxies NGC 147 And NGC 185
Contrary to a previously published claim it is found that the spheroidal
galaxies NGC 147 and NGC 185 probably form a stable binary system. Distance
estimates place this pair on the near side of the Andromeda subgroup of the
Local Group. The fact that this system has probably remained stable over a
Hubble time suggests that it does not have a plunging orbit that brings it very
close to M 31. It is noted that the only two Local Group galaxy pairs, in which
the components have comparable masses, also have similar morphological types.
NGC 147 and NGC 185 are both spheroidals, while the LMC and SMC are both
irregulars. This suggests that protogalaxies of similar mass that are spawned
in similar environments evolve into objects having similar morphologies.Comment: To be published in A.J. October 199
Morse theory on spaces of braids and Lagrangian dynamics
In the first half of the paper we construct a Morse-type theory on certain
spaces of braid diagrams. We define a topological invariant of closed positive
braids which is correlated with the existence of invariant sets of parabolic
flows defined on discretized braid spaces. Parabolic flows, a type of
one-dimensional lattice dynamics, evolve singular braid diagrams in such a way
as to decrease their topological complexity; algebraic lengths decrease
monotonically. This topological invariant is derived from a Morse-Conley
homotopy index and provides a gloablization of `lap number' techniques used in
scalar parabolic PDEs.
In the second half of the paper we apply this technology to second order
Lagrangians via a discrete formulation of the variational problem. This
culminates in a very general forcing theorem for the existence of infinitely
many braid classes of closed orbits.Comment: Revised version: numerous changes in exposition. Slight modification
of two proofs and one definition; 55 pages, 20 figure
Classical spin systems and the quantum stabilizer formalism: general mappings and applications
We present general mappings between classical spin systems and quantum
physics. More precisely, we show how to express partition functions and
correlation functions of arbitrary classical spin models as inner products
between quantum stabilizer states and product states, thereby generalizing
mappings for some specific models established in [Phys. Rev. Lett. 98, 117207
(2007)]. For Ising- and Potts-type models with and without external magnetic
field, we show how the entanglement features of the corresponding stabilizer
states are related to the interaction pattern of the classical model, while the
choice of product states encodes the details of interaction. These mappings
establish a link between the fields of classical statistical mechanics and
quantum information theory, which we utilize to transfer techniques and methods
developed in one field to gain insight into the other. For example, we use
quantum information techniques to recover well known duality relations and
local symmetries of classical models in a simple way, and provide new classical
simulation methods to simulate certain types of classical spin models. We show
that in this way all inhomogeneous models of q-dimensional spins with pairwise
interaction pattern specified by a graph of bounded tree-width can be simulated
efficiently. Finally, we show relations between classical spin models and
measurement-based quantum computation.Comment: 24 pages, 5 figures, minor corrections, version as accepted in JM
Qualitative Viscous Cosmology
The Full (non--truncated) Israel--Stewart theory of bulk viscosity is applied
to dissipative FRW spacetimes. Dimensionless variables and dimensionless
equations of state are used to write the Einstein--thermodynamic equations as a
plane autonomous system and the qualitative behaviour of this system is
determined. Entropy production in these models is also discussed.Comment: 13 pages, REVTeX, accepted for publication in Physical Review
Graph states as ground states of many-body spin-1/2 Hamiltonians
We consider the problem whether graph states can be ground states of local
interaction Hamiltonians. For Hamiltonians acting on n qubits that involve at
most two-body interactions, we show that no n-qubit graph state can be the
exact, non-degenerate ground state. We determine for any graph state the
minimal d such that it is the non-degenerate ground state of a d-body
interaction Hamiltonian, while we show for d'-body Hamiltonians H with d'<d
that the resulting ground state can only be close to the graph state at the
cost of H having a small energy gap relative to the total energy. When allowing
for ancilla particles, we show how to utilize a gadget construction introduced
in the context of the k-local Hamiltonian problem, to obtain n-qubit graph
states as non-degenerate (quasi-)ground states of a two-body Hamiltonian acting
on n'>n spins.Comment: 10 pages, 1 figur
Hard X-ray timing and spectral characteristics of the energetic pulsar PSR J0205+6449 in supernova remnant 3C58
PSR J0205+6449 is a young rotation-powered pulsar in SNR 3C 58. It is one of
only three young (<10,000 year old) pulsars which are so far detected in the
radio and the classical X-ray bands, as well as at hard X-rays above 20 keV and
at high-energy (>100 MeV) -rays. The other two young pulsars are the
Crab and PSR B1509-58. Our aim is to derive the timing and spectral
characteristics of PSR J0205+6449 over the broad X-ray band from ~0.5 to ~270
keV. We used all publicly available RXTE observations of PSR J0205+6449 to
first generate accurate ephemerides over the period September 30, 2000 - March
18, 2006. Next, phase-folding procedures yielded pulse profiles using data from
RXTE PCA and HEXTE, and XMM-Newton EPIC PN. While our timing solutions are
consistent with earlier results, our work shows sharper structures in the PCA
X-ray profile. The X-ray pulse profile consists of two sharp pulses, separated
in phase by 0.488(2), which can be described with 2 asymmetric Lorentzians,
each with the rising wing steeper than the trailing wing, and
full-width-half-maximum 1.41(5) ms and 2.35(22) ms, respectively. We find an
indication for a flux increase by a factor ~2, about 3.5 sigma above the
time-averaged value, for the second, weaker pulse during a two-week interval,
while its pulse shape did not change. The spectrum of the pulsed X-ray emission
is of non-thermal origin, exhibiting a power-law shape with photon index Gamma
= 1.03(2) over the energy band ~0.5 to ~270 keV. In the energy band covered
with the PCA (~3-30 keV) the spectra of the two pulses have the same photon
index, namely, 1.04(3) and 1.10(8), respectively.Comment: 10 pages; 7 figures (2 in color), resubmitted to A&A, including
referee comment
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