15,202 research outputs found
A Complementary Third Law for Black Hole Thermodynamics
There are some examples in the literature, in which despite the fact that the
underlying theory or model does not impose a lower bound on the size of black
holes, the final temperature under Hawking evaporation is nevertheless finite
and nonzero. We show that under some loose conditions, the black hole is
necessarily an effective remnant, in the sense that its evaporation time is
infinite. That is, the final state that there is nonzero finite temperature
despite having no black hole remaining cannot be realized. We discuss the
limitations, subtleties, and the implications of this result, which is
reminiscent of the third law of black hole thermodynamics, but with the roles
of temperature and size interchanged. We therefore refer to our result as the
"complementary third law" for black hole thermodynamics.Comment: 10 pages, 5 figures; improved and published versio
Tests for Cosmological Evolution of a Brane Universe Model
The relativistic Friedmann Lemaitre cosmology model (FLCM) is very sucessful
to describe the evolution history of the Universe from the " First three
Minutes". Any alternative model should be consistent with the FLCM explanations
to the later stage evolutions of the Universe at certain points. An noncompact
extra dimension model was recently proposed by Randall and Sundrum. Binetruy et
al. obtained the modified Friedmann equation, in which the energy density of
the brane appears quadratically in contrast with the linear behavior of the
standard Friedmann equation. We investigate kinds of classical cosmological
effects of the new models and get a general solution of the cosmic evolution
for this extended model, with more detail discussions of the brane tension
parameter on these cosmological tests.Comment: 12 pages, 5 figures, to appear in IJMP
Deciphering Charging Status, Absolute Quantum Efficiency, and Absorption Cross Section of MultiCarrier States in Single Colloidal Quantum Dot
Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often
found in multi-carrier states due to multi-photon absorption and photo-charging
of the QDs. While many of these multi-carrier states are observed in single-dot
spectroscopy, their properties are not well studied due to random
charging/discharging, emission intensity intermittency, and uncontrolled
surface defects of single QD. Here we report in-situ deciphering the charging
status, and precisely assessing the absorption cross section, and determining
the absolute emission quantum yield of mono-exciton and biexciton states for
neutral, positively-charged, and negatively-charged single core/shell CdSe/CdS
QD. We uncover very different photon statistics of the three charge states in
single QD and unambiguously identify their charge sign together with the
information of their photoluminescence decay dynamics. We then show their
distinct photoluminescence saturation behaviors and evaluated the absolute
values of absorption cross sections and quantum efficiencies of monoexcitons
and biexcitons. We demonstrate that addition of an extra hole or electron in a
QD changes not only its emission properties but also varies its absorption
cross section
Decoupling Dynamic Monocular Videos for Dynamic View Synthesis
The challenge of dynamic view synthesis from dynamic monocular videos, i.e.,
synthesizing novel views for free viewpoints given a monocular video of a
dynamic scene captured by a moving camera, mainly lies in accurately modeling
the dynamic objects of a scene using limited 2D frames, each with a varying
timestamp and viewpoint. Existing methods usually require pre-processed 2D
optical flow and depth maps by off-the-shelf methods to supervise the network,
making them suffer from the inaccuracy of the pre-processed supervision and the
ambiguity when lifting the 2D information to 3D. In this paper, we tackle this
challenge in an unsupervised fashion. Specifically, we decouple the motion of
the dynamic objects into object motion and camera motion, respectively
regularized by proposed unsupervised surface consistency and patch-based
multi-view constraints. The former enforces the 3D geometric surfaces of moving
objects to be consistent over time, while the latter regularizes their
appearances to be consistent across different viewpoints. Such a fine-grained
motion formulation can alleviate the learning difficulty for the network, thus
enabling it to produce not only novel views with higher quality but also more
accurate scene flows and depth than existing methods requiring extra
supervision
Soft-Defined Heterogeneous Vehicular Network: Architecture and Challenges
Heterogeneous Vehicular NETworks (HetVNETs) can meet various
quality-of-service (QoS) requirements for intelligent transport system (ITS)
services by integrating different access networks coherently. However, the
current network architecture for HetVNET cannot efficiently deal with the
increasing demands of rapidly changing network landscape. Thanks to the
centralization and flexibility of the cloud radio access network (Cloud-RAN),
soft-defined networking (SDN) can conveniently be applied to support the
dynamic nature of future HetVNET functions and various applications while
reducing the operating costs. In this paper, we first propose the multi-layer
Cloud RAN architecture for implementing the new network, where the multi-domain
resources can be exploited as needed for vehicle users. Then, the high-level
design of soft-defined HetVNET is presented in detail. Finally, we briefly
discuss key challenges and solutions for this new network, corroborating its
feasibility in the emerging fifth-generation (5G) era
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