47,869 research outputs found
Induced higher-derivative massive gravity on a 2-brane in 4D Minkowski space
In this paper we revisit the problem of localizing gravity in a 2-brane
embedded in a 4D Minkowski space to address induction of high derivative
massive gravity. We explore the structure of propagators to find well-behaved
higher-derivative massive gravity induced on the brane. Exploring a special
case in the generalized mass term of the graviton propagator we find a model of
consistent higher order gravity with an additional unitary massive spin-2
particle and two massless particles: one spin-0 particle and one spin-1
particle. The condition for the absence of tachyons is satisfied for both
`right' and `wrong' signs of the Einstein-Hilbert term on the 2-brane. We also
find the Pauli-Fierz mass term added to the new massive gravity in three
dimensions and recover the low dimensional DGP model.Comment: Latex, 12 pages, no figure; refs added, version to appear in PL
A Simple Business-Cycle Model with Schumpeterian Features
We develop a dynamic general equilibrium model of imperfect competition where a sunk cost of creating a new product regulates the type of entry that dominates in the economy: new products or more competition in existing industries. Considering the process of product innovation is irreversible, introduces hysteresis in the business cycle. Expansionary shocks may lead the economy to a new ‘prosperity plateau,’ but contractionary shocks only affect the market power of mature industriesEntry, Hysteresis, Mark-up
A Simple Business-Cycle Model with Schumpeterian Features
We develop a dynamic general equilibrium model of imperfect competition where a sunk cost of creating a new product regulates the type of entry that dominates in the economy: new products or more competition in existing industries. Considering the process of product innovation is irreversible, introduces hysteresis in the business cycle. Expansionary shocks may lead the economy to a new 'prosperity plateau,' but contractionary shocks only affect the market power of mature industries.Entry; hysteresis, mark-up
Effects of Random Biquadratic Couplings in a Spin-1 Spin-Glass Model
A spin-1 model, appropriated to study the competition between bilinear
(J_{ij}S_{i}S_{j}) and biquadratic (K_{ij}S_{i}^{2}S_{j}^{2}) random
interactions, both of them with zero mean, is investigated. The interactions
are infinite-ranged and the replica method is employed. Within the
replica-symmetric assumption, the system presents two phases, namely,
paramagnetic and spin-glass, separated by a continuous transition line. The
stability analysis of the replica-symmetric solution yields, besides the usual
instability associated with the spin-glass ordering, a new phase due to the
random biquadratic couplings between the spins.Comment: 16 pages plus 2 ps figure
Statistical Mechanics Characterization of Neuronal Mosaics
The spatial distribution of neuronal cells is an important requirement for
achieving proper neuronal function in several parts of the nervous system of
most animals. For instance, specific distribution of photoreceptors and related
neuronal cells, particularly the ganglion cells, in mammal's retina is required
in order to properly sample the projected scene. This work presents how two
concepts from the areas of statistical mechanics and complex systems, namely
the \emph{lacunarity} and the \emph{multiscale entropy} (i.e. the entropy
calculated over progressively diffused representations of the cell mosaic),
have allowed effective characterization of the spatial distribution of retinal
cells.Comment: 3 pages, 1 figure, The following article has been submitted to
Applied Physics Letters. If it is published, it will be found online at
http://apl.aip.org
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