1,238 research outputs found
Addressing the Debt Crisis in the European Union: The Validity of Mandatory Collective Action Clauses and Extended Maturities
The sovereign debt crisis in the European Union has put significant pressure on the fundamental divisions of power between the Union government and member states. One part of the recommended solution for the crisis calls for the imposition of mandatory collective action clauses and extended maturities for all sovereign bonds issued by member states, the first instances of Union-wide fiscal policy choices being forced upon member states. After an explanation of the relevant bond terms, this Comment evaluates the validity of the proposed mandates based on the current state of the framework of power in the EU and concludes that the mandates are valid under the EU implied powers doctrine. The Comment also explains why the acceptance or rejection of these bond-term mandates has the potential to lead to either the full integration or dissolution of the EU
Cosmological constant influence on cosmic string spacetime
We investigate the line element of spacetime around a linear cosmic string in
the presence of a cosmological constant. We obtain the metric and argue that it
should be discarded because of asymptotic considerations. Then a time dependent
and consistent form of the metric is obtained and its properties are discussed.Comment: 3 page
Open inflation and the singular boundary
The singularity in Hawking and Turok's model (hep-th/9802030) of open
inflation has some appealing properties. We suggest that this singularity
should be regularized with matter. The singular instanton can then be obtained
as the limit of a family of ``no-boundary'' solutions where both the geometry
and the scalar field are regular. Using this procedure, the contribution of the
singularity to the Euclidean action is just 1/3 of the Gibbons-Hawking boundary
term. Unrelated to this question, we also point out that gravitational
backreaction improves the behaviour of scalar perturbations near the
singularity. As a result, the problem of quantizing scalar perturbations and
gravity waves seems to be very well posed.Comment: 7 page
Topology from the Simulated Sloan Digital Sky Survey
We measure the topology (genus curve) of the galaxy distribution in a mock
redshift catalog designed to resemble the upcoming Sloan Digital Sky Survey
(SDSS). The catalog, drawn from a large N-body simulation of a Lambda-CDM cos-
mological model, mimics the anticipated spectroscopic selection procedures of
the SDSS in some detail. Sky maps, redshift slices, and 3-D contour maps of the
mock survey reveal a rich and complex structure, including networks of voids
and superclusters that resemble the patterns seen in the CfA redshift survey
and the Las Campanas Redshift Survey (LCRS). The 3-D genus curve can be
measured from the simulated catalog with superb precision; this curve has the
general shape predicted for Gaussian, random phase initial conditions, but the
error bars are small enough to demonstrate with high significance the subtle
departures from this shape caused by non-linear gravitational evolution. These
distortions have the form predicted by Matsubara's (1994) perturbative anal-
ysis, but they are much smaller in amplitude. We also measure the 3-D genus
curve of the radial peculiar velocity field measured by applying distance-
indicator relations (with realistic errors) to the mock catalog. This genus
curve is consistent with the Gaussian random phase prediction, though it is of
relatively low precision because of the large smoothing length required to
overcome noise in the measured velocity field. Finally, we measure the 2-D
topology in redshift slices, similar to early slices from the SDSS and to
slices already observed in the LCRS. The genus curves of these slices are
consistent with the observed genus curves of the LCRS, providing further
evidence in favor of the inflationary CDM model with Omega_M~0.4. The catalog
is publicly available at http://www.astronomy.ohio-state.edu/~dhw/sdss.html.Comment: ASTeX 4.0 Preprint Style, 5 GIF figures (Figs 1, 2, 3a, 3b, 6; see
http://cfa-www.harvard.edu/~wcolley/SDSS_Top/ for PostScript versions), 7
PostScript figures. Figure 5 and Table 1 have minor corrections since
publicatio
Self-Dual Chern-Simons Solitons in (2+1)-Dimensional Einstein Gravity
We consider here a generalization of the Abelian Higgs model in curved space,
by adding a Chern--Simons term. The static equations are self-dual provided we
choose a suitable potential. The solutions give a self-dual
Maxwell--Chern--Simons soliton that possesses a mass and a spin
Exact Relativistic Two-Body Motion in Lineal Gravity
We consider the N-body problem in (1+1) dimensional lineal gravity. For 2
point masses (N=2) we obtain an exact solution for the relativistic motion. In
the equal mass case we obtain an explicit expression for their proper
separation as a function of their mutual proper time. Our solution gives the
exact Hamiltonian to infinite order in the gravitational coupling constant.Comment: latex, 11 pages, 2 figures, final version to appear in Phys. Rev.
Let
Mass of Clusters in Simulations
We show that dark matter haloes, in n--body simulations, have a boundary
layer (BL) with precise features. In particular, it encloses all dynamically
stable mass while, outside it, dynamical stability is lost soon. Particles can
pass through such BL, which however acts as a confinement barrier for dynamical
properties. BL is set by evaluating kinetic and potential energies (T(r) and
W(r)) and calculating R=-2T/W. Then, on BL, R has a minimum which closely
approaches a maximum of w= -dlog W/dlog r. Such ``requirement'' is
consistent with virial equilibrium, but implies further regularities. We test
the presence of a BL around haloes in spatially flat CDM simulations, with or
without cosmological constant. We find that the mass M_c, enclosed within the
radius r_c, where the requirement is fulfilled, closely approaches the
mass M_{dyn}, evaluated from the velocities of all particles within r_c,
according to the virial theorem. Using r_c we can then determine an individual
density contrast Delta_c for each virialized halo, which can be compared with
the "virial" density contrast (Omega_m: matter
density parameter) obtained assuming a spherically symmetric and unperturbed
fluctuation growth. The spread in Delta_c is wide, and cannot be neglected when
global physical quantities related to the clusters are calculated, while the
average Delta_c is ~25 % smaller than the corresponding Delta_v; moreover if
is defined from the radius linked to Delta_v, we have a much worse
fit with particle mass then starting from {\it Rw} requirement.Comment: 4 pages, 5 figures, contribution to the XXXVIIth Rencontres de
Moriond, The Cosmological Model, Les Arc March 16-23 2002, to appear in the
proceeding
Vortices in Bogomol'nyi Limit of Einstein Maxwell Higgs Theory with or without External Sources
The Abelian Higgs model with or without external particles is considered in
curved space. Using the dual transformation, we rewrite the model in terms of
dual gauge fields and derive the Bogomol'nyi-type bound. We examine
cylindrically symmetric solutions to Einstein equations and the first-order
Bogomol'nyi equations, and find vortex solutions and vortex-particle composites
which lie on the spatial manifold with global geometry described by a cylinder
asymptotically or a two sphere in addition to the well-known cone.Comment: LaTeX, 23 pages, 10 LaTeX figures included, KHTP-93-05, SNUTP-93-100,
DPNU-93-46. (A note and several references added
Polarization Correlations in Pair Production from Charged and Neutral Strings
Polarization correlations of pair productions from charged and
neutral Nambu strings are investigated, via photon and graviton emissions,
respectively and explicit expressions for their corresponding probabilities are
derived and found to be \textit{speed} dependent. The strings are taken to be
circularly oscillating closed strings, as perhaps the simplest solution of the
Nambu action. In the extreme relativistic case, these probabilities coincide,
but, in general, are different, and such inquiries, in principle, indicate
whether the string is charged or uncharged. It is remarkable that these
dynamical relativistic quantum field theory calculations lead to a clear
violation of Local Hidden Variables theories.Comment: 6 pages, no figure, LaTeX with ws-mpla.cl
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