29,209 research outputs found
Testing the Lorentz and CPT Symmetry with CMB polarizations and a non-relativistic Maxwell Theory
We present a model for a system involving a photon gauge field and a scalar
field at quantum criticality in the frame of a Lifthitz-type non-relativistic
Maxwell theory. We will show this model gives rise to Lorentz and CPT violation
which leads to a frequency-dependent rotation of polarization plane of
radiations, and so leaves potential signals on the cosmic microwave background
temperature and polarization anisotropies.Comment: 7 pages, 2 figures, accepted on JCAP, a few references adde
A novel approach for the assessment of morphological evolution based on observed water levels in tide-dominated estuaries
Assessing the impacts of both natural (e.g., tidal forcing from the ocean) and human-induced changes (e.g., dredging for navigation, land reclamation) on estuarine morphology is particularly important for the protection and management of the estuarine environment. In this study, a novel analytical approach is proposed for the assessment of estuarine morphological evolution in terms of tidally averaged depth on the basis of the observed water levels along the estuary. The key lies in deriving a relationship between wave celerity and tidal damping or amplification. For given observed water levels at two gauging stations, it is possible to have a first estimation of both wave celerity (distance divided by tidal travelling time) and tidal damping or amplification rate (tidal range difference divided by distance), which can then be used to predict the morphological changes via an inverse analytical model for tidal hydrodynamics. The proposed method is applied to the Lingdingyang Bay of the Pearl River Estuary, located on the southern coast of China, to analyse the historical development of the tidal hydrodynamics and morphological evolution. The analytical results show surprisingly good correspondence with observed water depth and volume in this system. The merit of the proposed method is that it provides a simple approach for understanding the decadal evolution of the estuarine morphology through the use of observed water levels, which are usually available and can be easily measured.National Key R&D of China (Grant No.
2016YFC0402601), National Natural Science Foundation of China (Grant No. 51979296, 51709287,
41706088, 41476073), Fundamental Research Funds for the Central Universities (No.18lgpy29)
and from the Water Resource Science and Technology Innovation Program of Guangdong Province (Grant
No. 2016-20, 2016-21). The work of the second author was supported by FCT research contracts
IF/00661/2014/CP1234.info:eu-repo/semantics/submittedVersio
Bounce and cyclic cosmology in extended nonlinear massive gravity
We investigate non-singular bounce and cyclic cosmological evolutions in a
universe governed by the extended nonlinear massive gravity, in which the
graviton mass is promoted to a scalar-field potential. The extra freedom of the
theory can lead to certain energy conditions violations and drive cyclicity
with two different mechanisms: either with a suitably chosen scalar-field
potential under a given Stuckelberg-scalar function, or with a suitably chosen
Stuckelberg-scalar function under a given scalar-field potential. Our analysis
shows that extended nonlinear massive gravity can alter significantly the
evolution of the universe at both early and late times.Comment: 20 pages, 5 figures, version published at JCA
Red and orange laser operation of Pr:KYF4 pumped by a Nd:YAG/LBO laser at 469.1nm and a InGaN laser diode at 444nm
We report the basic luminescence properties and the continuous-wave (CW) laser operation of a Pr3+-doped KYF4 single crystal in the Red and Orange spectral regions by using a new pumping scheme. The pump source is an especially developed, compact, slightly tunable and intra-cavity frequency-doubled diode-pumped Nd:YAG laser delivering a CW output power up to about 1.4 W around 469.1 nm. At this pump wavelength, red and orange laser emissions are obtained at about 642.3 and 605.5 nm, with maximum output powers of 11.3 and 1 mW and associated slope efficiencies of 9.3% and 3.4%, with respect to absorbed pump powers, respectively. For comparison, the Pr:KYF4 crystal is also pumped by a InGaN blue laser diode operating around 444 nm. In this case, the same red and orange lasers are obtained, but with maximum output powers of 7.8 and 2 mW and the associated slope efficiencies of 7 and 5.8%, respectively. Wavelength tuning for the two lasers is demonstrated by slightly tilting the crystal. Orange laser operation and laser wavelength tuning are reported for the first time
Parton Distributions at Hadronization from Bulk Dense Matter Produced at RHIC
We present an analysis of , , and spectra from
Au+Au collisions at GeV in terms of distributions of
effective constituent quarks at hadronization. Consistency in quark ratios
derived from various hadron spectra provides clear evidence for hadron
formation dynamics as suggested by quark coalescence or recombination models.
We argue that the constituent quark distribution reflects properties of the
effective partonic degrees of freedom at hadronization. Experimental data
indicate that strange quarks have a transverse momentum distribution flatter
than that of up/down quarks consistent with hydrodynamic expansion in partonic
phase prior to hadronization. After the AMPT model is tuned to reproduce the
strange and up/down quark distributions, the model can describe the measured
spectra of hyperons and mesons very well where hadrons are formed
through dynamical coalescence.Comment: 5 pages, 3 figures, two more paragraph added to address the referee's
comment, figure updated to include the KET scale. Accepted version to appear
in Phys. Rev.
NFV service dynamicity with a DevOps approach : demonstrating zero-touch deployment & operations
Next generation network services will be realized by NFV-based microservices to enable greater dynamics in deployment and operations. Here, we present a demonstrator that realizes this concept using the NFV platform built in the EU FP7 project UNIFY. Using the example of an Elastic Router service, we show automated deployment and configuration of service components as well as corresponding monitoring components facilitating automated scaling of the entire service. We also demonstrate automatic execution of troubleshooting and debugging actions. Operations of the service are inspired by DevOps principles, enabling quick detection of operational conditions and fast corrective actions. This demo conveys essential insights on how the life-cycle of an NFV-based network service may be realized in future NFV platforms
Possibility of cyclic Turnarounds In Brane-world Scenario: Phantom Energy Accretion onto Black Holes and its consequences
A universe described by braneworlds is studied in a cyclic scenario. As
expected such an oscillating universe will undergo turnarounds, whenever the
phantom energy density reaches a critical value from either side. It is found
that a universe described by RSII brane model will readily undergo oscillations
if, either the brane tension, \lambda, or the bulk cosmological constant,
\Lambda_{4}, is negative. The DGP brane model does not readily undergo cyclic
turnarounds. Hence for this model a modified equation is proposed to
incorporate the cyclic nature. It is found that there is always a remanent mass
of a black hole at the verge of a turnaround. Hence contrary to known results
in literature, it is found that the destruction of black holes at the
turnaround is completely out of question. Finally to alleviate, if not solve,
the problem posed by the black holes, it is argued that the remanent masses of
the black holes do not act as a serious defect of the model because of Hawking
evaporation.Comment: 10 pages, 2 figures; International Journal of Theoretical Physics
(2012
Electromagnetic multipole theory for optical nanomaterials
Optical properties of natural or designed materials are determined by the
electromagnetic multipole moments that light can excite in the constituent
particles. In this work we present an approach to calculate the multipole
excitations in arbitrary arrays of nanoscatterers in a dielectric host medium.
We introduce a simple and illustrative multipole decomposition of the electric
currents excited in the scatterers and link this decomposition to the classical
multipole expansion of the scattered field. In particular, we find that
completely different multipoles can produce identical scattered fields. The
presented multipole theory can be used as a basis for the design and
characterization of optical nanomaterials
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