2,643 research outputs found
Expansive actions on uniform spaces and surjunctive maps
We present a uniform version of a result of M. Gromov on the surjunctivity of
maps commuting with expansive group actions and discuss several applications.
We prove in particular that for any group and any field \K, the
space of -marked groups such that the group algebra \K[G] is
stably finite is compact.Comment: 21 page
Modified Regge calculus as an explanation of dark energy
Using Regge calculus, we construct a Regge differential equation for the time
evolution of the scale factor in the Einstein-de Sitter cosmology model
(EdS). We propose two modifications to the Regge calculus approach: 1) we allow
the graphical links on spatial hypersurfaces to be large, as in direct particle
interaction when the interacting particles reside in different galaxies, and 2)
we assume luminosity distance is related to graphical proper distance
by the equation , where the inner product can differ from its usual
trivial form. The modified Regge calculus model (MORC), EdS and CDM
are compared using the data from the Union2 Compilation, i.e., distance moduli
and redshifts for type Ia supernovae. We find that a best fit line through
versus gives a correlation of
0.9955 and a sum of squares error (SSE) of 1.95. By comparison, the best fit
CDM gives SSE = 1.79 using = 69.2 km/s/Mpc, = 0.29
and = 0.71. The best fit EdS gives SSE = 2.68 using =
60.9 km/s/Mpc. The best fit MORC gives SSE = 1.77 and = 73.9 km/s/Mpc
using = 8.38 Gcy and kg, where is the
current graphical proper distance between nodes, is the scaling factor
from our non-trival inner product, and is the nodal mass. Thus, MORC
improves EdS as well as CDM in accounting for distance moduli and
redshifts for type Ia supernovae without having to invoke accelerated
expansion, i.e., there is no dark energy and the universe is always
decelerating.Comment: 15 pages text, 6 figures. Revised as accepted for publication in
Class. Quant. Gra
Welfare loss with municipal amalgamations and the willingness-to-pay for the municipality name
Functional advantages and drawbacks are commonly mentioned to rationally justify or condemn municipality amalgamations. However, many consolidation projects are resisted by local governments or citizens on the grounds that amalgamation would dampen local identity. A municipality's name change is probably the most visible sign of the loss of community bond experienced by citizens at amalgamation time. This article aims to put a value on this loss by measuring citizen willingness to pay for their city name. This methodological approach innovates upon the literature on municipal amalgamation and place branding by exploiting the versatility of the so-called contingent valuation method (CVM). CVM confronts respondents, in a survey setting, with a hypothetical market in which a characteristic of interest is exchanged. Here the characteristic is the possibility to retain one's city name for an amalgamated jurisdiction. The article presents the estimates provided by a survey conducted in four Swiss cities
Ex-post survey on the consequences and perceptions about amalgamation : The case of two Swiss municipalities
In 2006, two municipalities located in the canton of Fribourg (Switzerland), La Tour-de-Trême and Bulle, amalgamated. In this study, we report on the evolution of citizen perceptions as well as try to better understand the reasons behind the respondents various positions concerning this new political and territorial entity. Five-hundred individuals were surveyed almost four years after the amalgamation came into effect. Our results show that if the amalgamation was voted again, it would be necessary to be particularly attentive to citizen access to municipal offices and to local service provisions, to citizen identification to their municipality as well as to the life of the local associations. Indeed, these are clearly important issues for small localities. Furthermore, citizens of the newly amalgamated municipality are mostly sensitive to access to municipal offices and to contact with local representatives. Improving the population's perceptions of these particular issues could lead to a 12 percentage point increase in support for the amalgamation
Maxwell equations in matrix form, squaring procedure, separating the variables, and structure of electromagnetic solutions
The Riemann -- Silberstein -- Majorana -- Oppenheimer approach to the Maxwell
electrodynamics in vacuum is investigated within the matrix formalism. The
matrix form of electrodynamics includes three real 4 \times 4 matrices. Within
the squaring procedure we construct four formal solutions of the Maxwell
equations on the base of scalar Klein -- Fock -- Gordon solutions. The problem
of separating physical electromagnetic waves in the linear space
\lambda_{0}\Psi^{0}+\lambda_{1}\Psi^{1}+\lambda_{2}\Psi^{2}+ lambda_{3}\Psi^{3}
is investigated, several particular cases, plane waves and cylindrical waves,
are considered in detail.Comment: 26 pages 16 International Seminar NCPC, May 19-22, 2009, Minsk,
Belaru
Generalized Gravi-Electromagnetism
A self consistant and manifestly covariant theory for the dynamics of four
charges (masses) (namely electric, magnetic, gravitational, Heavisidian) has
been developed in simple, compact and consistent manner. Starting with an
invariant Lagrangian density and its quaternionic representation, we have
obtained the consistent field equation for the dynamics of four charges. It has
been shown that the present reformulation reproduces the dynamics of individual
charges (masses) in the absence of other charge (masses) as well as the
generalized theory of dyons (gravito - dyons) in the absence gravito - dyons
(dyons). key words: dyons, gravito - dyons, quaternion PACS NO: 14.80H
Exponential beams of electromagnetic radiation
We show that in addition to well known Bessel, Hermite-Gauss, and
Laguerre-Gauss beams of electromagnetic radiation, one may also construct
exponential beams. These beams are characterized by a fall-off in the
transverse direction described by an exponential function of rho. Exponential
beams, like Bessel beams, carry definite angular momentum and are periodic
along the direction of propagation, but unlike Bessel beams they have a finite
energy per unit beam length. The analysis of these beams is greatly simplified
by an extensive use of the Riemann-Silberstein vector and the Whittaker
representation of the solutions of the Maxwell equations in terms of just one
complex function. The connection between the Bessel beams and the exponential
beams is made explicit by constructing the exponential beams as wave packets of
Bessel beams.Comment: Dedicated to the memory of Edwin Powe
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