4,496 research outputs found
Dark-Matter Decays and Self-Gravitating Halos
We consider models in which a dark-matter particle decays to a slightly less
massive daughter particle and a noninteracting massless particle. The decay
gives the daughter particle a small velocity kick. Self-gravitating dark-matter
halos that have a virial velocity smaller than this velocity kick may be
disrupted by these particle decays, while those with larger virial velocities
will be heated. We use numerical simulations to follow the detailed evolution
of the total mass and density profile of self-gravitating systems composed of
particles that undergo such velocity kicks as a function of the kick speed
(relative to the virial velocity) and the decay time (relative to the dynamical
time). We show how these decays will affect the halo mass-concentration
relation and mass function. Using measurements of the halo mass-concentration
relation and galaxy-cluster mass function to constrain the
lifetime--kick-velocity parameter space for decaying dark matter, we find
roughly that the observations rule out the combination of kick velocities
greater than 100 km/s and decay times less than a few times the age of the
Universe.Comment: 17 pages, 10 figures, replaced with published versio
Assessing the Political Impacts of a Conditional Cash Transfer: Evidence From a Randomized Policy Experiment in Indonesia
Several developing nations, including Indonesia, have experimented with conditional cash transfers (ccts) to poor households during recent years. since 2007, Indonesia has been carrying out a randomized cct pilot program (pnpm generasi) in 1,625 villages where funds are disbursed to communities rather than households, and local councils allocate the funds to public projects following community input. in this paper, we explore political outcomes associated with the program, including electoral rewards for incumbents, and political participation. by comparing regions receiving the program with a control group, we estimate the cct\u27s effects on political behavior in the 2009 elections for president and the national legislative assembly, and we also explore its effects on local politics. we find that the cct program increases vote shares for legislative candidates from the incumbent president\u27s party, improves households\u27 satisfaction with kabupaten-level government administrative services, and decreases competition among presidential candidates as measured by the herfindahl-hirschman index (hhi). we do not find conclusive evidence to support the hypothesis that the program increases votes for the incumbent president, and we find no evidence that the program significantly increases voter turnout or affects village-level politics.
keywords: conditional cash transfer, political behavior, Indonesi
Energetic perspective on emergent inductance exhibited by magnetic textures in the pinned regime
Spatially varying magnetic textures can exhibit electric-current-induced
dynamics as a result of the spin-transfer torque effect. When such a magnetic
system is electrically driven, an electric field is generated, which is called
the emergent electric field. In particular, when magnetic-texture dynamics are
induced under the application of an AC electric current, the emergent electric
field also appears in an AC manner, notably, with an out-of-phase time profile,
thus exhibiting inductor behaviour, often called an emergent inductor. Here we
show that the emergent inductance exhibited by magnetic textures in the pinned
regime can be explained in terms of the current-induced energy stored in the
magnetic system. We numerically find that the inductance values defined from
the emergent electric field and the current-induced magnetization-distortion
energy, respectively, are in quantitative agreement in the so-called adiabatic
limit. Our findings indicate that emergent inductors retain the basic concept
of conventional inductors; that is, the energy is stored under the application
of electric current
Affine extension of noncrystallographic Coxeter groups and quasicrystals
Unique affine extensions H^{\aff}_2, H^{\aff}_3 and H^{\aff}_4 are
determined for the noncrystallographic Coxeter groups , and .
They are used for the construction of new mathematical models for quasicrystal
fragments with 10-fold symmetry. The case of H^{\aff}_2 corresponding to
planar point sets is discussed in detail. In contrast to the cut-and-project
scheme we obtain by construction finite point sets, which grow with a model
specific growth parameter.Comment: (27 pages, to appear in J. Phys. A
On the effect of Ti on Oxidation Behaviour of a Polycrystalline Nickel-based Superalloy
Titanium is commonly added to nickel superalloys but has a well-documented
detrimental effect on oxidation resistance. The present work constitutes the
first atomistic-scale quantitative measurements of grain boundary and bulk
compositions in the oxide scale of a current generation polycrystalline nickel
superalloy performed through atom probe tomography. Titanium was found to be
particularly detrimental to oxide scale growth through grain boundary
diffusion
Effective Field Theory Program for Conformal Quantum Anomalies
The emergence of conformal states is established for any problem involving a
domain of scales where the long-range, SO(2,1) conformally invariant
interaction is applicable. Whenever a clear-cut separation of ultraviolet and
infrared cutoffs is in place, this renormalization mechanism produces binding
in the strong-coupling regime. A realization of this phenomenon, in the form of
dipole-bound anions, is discussed.Comment: 15 pages. Expanded, with additional calculational details. To be
published in Phys. Rev.
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