2,279 research outputs found
Observational constraints on theory
The theory, which is an extension of teleparallel, or torsion scalar
, gravity, is recently proposed to explain the present cosmic accelerating
expansion with no need of dark energy. In this Letter, we first perform the
statefinder analysis and diagnostic to two concrete models,
i.e., and , and find that
a crossing of phantom divide line is impossible for both models. This is
contrary to an existing result where a crossing is claimed for the second
model. We, then, study the constraints on them from the latest Union 2 Type Ia
Supernova (Sne Ia) set, the baryonic acoustic oscillation (BAO), and the cosmic
microwave background (CMB) radiation. Our results show that at the 95%
confidence level ,
for Model 1 and ,
for Model 2. A comparison of these two models with
the CDM by the (dof: degree of freedom) criterion
indicates that CDM is still favored by observations. We also study the
evolution of the equation of state for the effective dark energy in the theory
and find that Sne Ia favors a phantom-like dark energy, while Sne Ia + BAO +
CMB prefers a quintessence-like one.Comment: 15 pages, 5 figures; statefinder diagnostic added, Om(z) analysis
added; references added; accepted by PL
The dynamical behavior of theory
Recently, a new model obtained from generalizing teleparallel gravity, named
theory, is proposed to explain the present cosmic accelerating expansion
with no need of dark energy. In this paper, we analyze the dynamical property
of this theory. For a concrete power law model, we obtain that the dynamical
system has a stable de Sitter phase along with an unstable radiation dominated
phase and an unstable matter dominated one. We show that the Universe can
evolve from a radiation dominated era to a matter dominated one, and finally
enter an exponential expansion phase.Comment: 10 pages, 1 figure; accepted by PL
Emergent universe from the Ho\v{r}ava-Lifshitz gravity
We study the stability of the Einstein static universe in the
Ho\v{r}ava-Lifshitz (HL) gravity and a generalized version of it formulated by
Sotiriou, Visser and Weifurtner. We find that, for the HL cosmology, there
exists a stable Einstein static state if the cosmological constant is
negative. The universe can stay at this stable state eternally and thus the big
bang singularity can be avoided. However, in this case, the Universe can not
exit to an inflationary era. For the Sotiriou, Visser and Weifurtner HL
cosmology, if the cosmic scale factor satisfies certain conditions initially,
the Universe can stay at the stable state past eternally and may undergo a
series of infinite, nonsingular oscillations. Once the parameter of the
equation of state approaches a critical value, the stable critical point
coincides with the unstable one, and the Universe enters an inflationary era.
Therefore, the big bang singularity can be avoided and a subsequent inflation
can occur naturally.Comment: 23 pages, 11 figures and 3 tables; title changed,comprehensive
analysis added, published versio
Multirole Logic (Extended Abstract)
We identify multirole logic as a new form of logic in which
conjunction/disjunction is interpreted as an ultrafilter on the power set of
some underlying set (of roles) and the notion of negation is generalized to
endomorphisms on this underlying set. We formalize both multirole logic (MRL)
and linear multirole logic (LMRL) as natural generalizations of classical logic
(CL) and classical linear logic (CLL), respectively, and also present a
filter-based interpretation for intuitionism in multirole logic. Among various
meta-properties established for MRL and LMRL, we obtain one named multiparty
cut-elimination stating that every cut involving one or more sequents (as a
generalization of a (binary) cut involving exactly two sequents) can be
eliminated, thus extending the celebrated result of cut-elimination by Gentzen
The thermalization of a two-level atom in a planar dielectric system out of thermal equilibrium
We study the thermalization of an elementary quantum system modeled by a
two-level atom interacting with stationary electromagnetic fields out of
thermal equilibrium near a dielectric slab. The slab is held at a temperature
different from that of the region where the atom is located. We find that when
the slab is a nonabsorbing and nondispersive dielectric of a finite thickness , no out of thermal equilibrium effects appear as far as the thermalization
of the atom is concerned, and a finite thick dielectric slab with a tiny
imaginary part in the relative permittivity
behaves like a half space dielectric substrate if is
satisfied, where is the transition wavelength of the atom. This
condition can serve as a guide for an experimental verification, using a
dielectric substrate of a finite thickness, of the effects that arise from out
of thermal equilibrium fluctuations with a half-space (infinite thickness)
dielectric.Comment: 15 pages, 2 figures, to appear in PR
Dynamical Universal Behavior in Quantum Chaotic Systems
We discover numerically that a moving wave packet in a quantum chaotic
billiard will always evolve into a quantum state, whose density probability
distribution is exponential. This exponential distribution is found to be
universal for quantum chaotic systems with rigorous proof. In contrast, for the
corresponding classical system, the distribution is Gaussian. We find that the
quantum exponential distribution can smoothly change to the classical Gaussian
distribution with coarse graining.Comment: 4 figure
Linearly Typed Dyadic Group Sessions for Building Multiparty Sessions
Traditionally, each party in a (dyadic or multiparty) session implements
exactly one role specified in the type of the session. We refer to this kind of
session as an individual session (i-session). As a generalization of i-session,
a group session (g-session) is one in which each party may implement a group of
roles based on one channel. In particular, each of the two parties involved in
a dyadic g-session implements either a group of roles or its complement. In
this paper, we present a formalization of g-sessions in a multi-threaded
lambda-calculus (MTLC) equipped with a linear type system, establishing for the
MTLC both type preservation and global progress. As this formulated MTLC can be
readily embedded into ATS, a full-fledged language with a functional
programming core that supports both dependent types (of DML-style) and linear
types, we obtain a direct implementation of linearly typed g-sessions in ATS.
The primary contribution of the paper lies in both of the identification of
g-sessions as a fundamental building block for multiparty sessions and the
theoretical development in support of this identification.Comment: This paper can be seen as the pre-sequel to classical linear
multirole logic (CLML). arXiv admin note: substantial text overlap with
arXiv:1603.0372
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