190 research outputs found
On the growth of perturbations in interacting dark energy and dark matter fluids
The covariant generalizations of the background dark sector coupling
suggested in G. Mangano, G. Miele and V. Pettorino, Mod. Phys. Lett. A 18, 831
(2003) are considered. The evolution of perturbations is studied with detailed
attention to interaction rate that is proportional to the product of dark
matter and dark energy densities. It is shown that some classes of models with
coupling of this type do not suffer from early time instabilities in strong
coupling regime.Comment: 11 pages, 2 figures. v3: minor changes, typos fixe
The imprint of the interaction between dark sectors in galaxy clusters
Based on perturbation theory, we study the dynamics of how dark matter and
dark energy in the collapsing system approach dynamical equilibrium while
interacting. We find that the interaction between dark sectors cannot ensure
the dark energy to fully cluster along with dark, leading to the energy
non-conservation problem in the collapsing system We examine the cluster number
counts dependence on the interaction between dark sectors. Furthermore, we
analyze how dark energy inhomogeneities affect cluster abundances. It is shown
that cluster number counts can provide specific signature of dark sectors
interaction and dark energy inhomogeneities.Comment: revised version. New treatment has been provided on studying the
structure formation in the spherical collapsing system where DE does not
cluster together with DM. Accepted for publication in JCA
The imprint of the interaction between dark sectors in galaxy clusters
Based on perturbation theory, we study the dynamics of how dark matter and
dark energy in the collapsing system approach dynamical equilibrium while
interacting. We find that the interaction between dark sectors cannot ensure
the dark energy to fully cluster along with dark, leading to the energy
non-conservation problem in the collapsing system We examine the cluster number
counts dependence on the interaction between dark sectors. Furthermore, we
analyze how dark energy inhomogeneities affect cluster abundances. It is shown
that cluster number counts can provide specific signature of dark sectors
interaction and dark energy inhomogeneities.Comment: revised version. New treatment has been provided on studying the
structure formation in the spherical collapsing system where DE does not
cluster together with DM. Accepted for publication in JCA
Effects of dark sectors' mutual interaction on the growth of structures
We present a general formalism to study the growth of dark matter
perturbations when dark energy perturbations and interactions between dark
sectors are present. We show that dynamical stability of the growth of
structure depends on the type of coupling between dark sectors. By taking the
appropriate coupling to ensure the stable growth of structure, we observe that
the effect of the dark sectors' interaction overwhelms that of dark energy
perturbation on the growth function of dark matter perturbation. Due to the
influence of the interaction, the growth index can differ from the value
without interaction by an amount within the observational sensibility, which
provides a possibility to disclose the interaction between dark sectors through
future observations on the growth of large structure.Comment: 15 pages, 4 figures, revised version, to appear in JCA
The new resilience of emerging and developing countries: systemic interlocking, currency swaps and geoeconomics
The vulnerability/resilience nexus that defined the interaction between advanced and developing economies in the post-WWII era is undergoing a fundamental transformation. Yet, most of the debate in the current literature is focusing on the structural constraints faced by the Emerging and Developing Countries (EDCs) and the lack of changes in the formal structures of global economic governance. This paper challenges this literature and its conclusions by focusing on the new conditions of systemic interlocking between advanced and emerging economies, and by analysing how large EDCs have built and are strengthening their economic resilience. We find that a significant redistribution of âpolicy spaceâ between advanced and emerging economies have taken place in the global economy. We also find that a number of seemingly technical currency swap agreements among EDCs have set in motion changes in the very structure of global trade and finance. These developments do not signify the end of EDCsâ vulnerability towards advanced economies. They signify however that the economic and geoeconomic implications of this vulnerability have changed in ways that constrain the options available to advanced economies and pose new challenges for the post-WWII economic order
Coupled dark matter-dark energy in light of near Universe observations
Cosmological analysis based on currently available observations are unable to
rule out a sizeable coupling among the dark energy and dark matter fluids. We
explore a variety of coupled dark matter-dark energy models, which satisfy
cosmic microwave background constraints, in light of low redshift and near
universe observations. We illustrate the phenomenology of different classes of
dark coupling models, paying particular attention in distinguishing between
effects that appear only on the expansion history and those that appear in the
growth of structure. We find that while a broad class of dark coupling models
are effectively models where general relativity (GR) is modified --and thus can
be probed by a combination of tests for the expansion history and the growth of
structure--, there is a class of dark coupling models where gravity is still
GR, but the growth of perturbations is, in principle modified. While this
effect is small in the specific models we have considered, one should bear in
mind that an inconsistency between reconstructed expansion history and growth
may not uniquely indicate deviations from GR. Our low redshift constraints
arise from cosmic velocities, redshift space distortions and dark matter
abundance in galaxy voids. We find that current data constrain the
dimensionless coupling to be |xi|<0.2, but prospects from forthcoming data are
for a significant improvement. Future, precise measurements of the Hubble
constant, combined with high-precision constraints on the growth of structure,
could provide the key to rule out dark coupling models which survive other
tests. We shall exploit as well weak equivalence principle violation arguments,
which have the potential to highly disfavour a broad family of coupled models.Comment: 34 pages, 6 figures; changes to match published versio
Reconstructing interacting new agegraphic polytropic gas model in non-flat FRW universe
We study the correspondence between the interacting new agegraphic dark
energy and the polytropic gas model of dark energy in the non-flat FRW
universe. This correspondence allows to reconstruct the potential and the
dynamics for the scalar field of the polytropic model, which describe
accelerated expansion of the universe.Comment: 9 page
Dissecting the impact of innovation on exporting in Turkey
Does innovating promote firms' export probability? By separately modelling - theoretically as well as empirically - the impact of process and product innovation, we show that the joint adoption of both innovation strategies fosters Turkish firms' first time export entry in rich destination markets. Nevertheless, innovation strengthens firms' export probability. As predicted by our theoretical sketch, product innovation matters in particular for exporting to developing economies, while process innovation reinforces the role of product innovation for exporting to richer markets
The generalized second law for the interacting generalized Chaplygin gas model
We investigate the validity of the generalized second law (GSL) of
gravitational thermodynamics in a non-flat FRW universe containing the
interacting generalized Chaplygin gas with the baryonic matter. The dynamical
apparent horizon is assumed to be the boundary of the universe. We show that
for the interacting generalized Chaplygin gas as a unified candidate for dark
matter (DM) and dark energy (DE), the equation of state parameter can cross the
phantom divide. We also present that for the selected model under thermal
equilibrium with the Hawking radiation, the GSL is always satisfied throughout
the history of the universe for any spatial curvature, independently of the
equation of state of the interacting generalized Chaplygin gas model.Comment: 8 page
Interacting entropy-corrected new agegraphic dark energy in Brans-Dicke cosmology
Motivated by a recent work of one of us [1], we extend it by using quantum
(or entropy) corrected new agegraphic dark energy in the Brans-Dicke cosmology.
The correction terms are motivated from the loop quantum gravity which is one
of the competitive theories of quantum gravity. Taking the non-flat background
spacetime along with the conformal age of the universe as the length scale, we
derive the dynamical equation of state of dark energy and the deceleration
parameter. An important consequence of this study is the phantom divide
scenario with entropy-corrected new agegraphic dark energy. Moreover, we assume
a system of dark matter, radiation and dark energy, while the later interacts
only with dark matter. We obtain some essential expressions related with dark
energy dynamics. The cosmic coincidence problem is also resolved in our model.Comment: 16 pages, no figure, accepted for publication in Gen. Relativ. Gra
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