507 research outputs found
Technically natural dark energy from Lorentz breaking
We construct a model of dark energy with a technically natural small
contribution to cosmic acceleration, i.e. this contribution does not receive
corrections from other scales in the theory. The proposed acceleration
mechanism appears generically in the low-energy limit of gravity theories with
violation of Lorentz invariance that contain a derivatively coupled scalar
field Theta. The latter may be the Goldstone field of a broken global symmetry.
The model, that we call Theta-CDM, is a valid effective field theory up to a
high cutoff just a few orders of magnitude below the Planck scale. Furthermore,
it can be ultraviolet-completed in the context of Horava gravity. We discuss
the observational predictions of the model. Even in the absence of a
cosmological constant term, the expansion history of the Universe is
essentially indistinguishable from that of Lambda-CDM. The difference between
the two theories appears at the level of cosmological perturbations. We find
that in Theta-CDM the matter power spectrum is enhanced at subhorizon scales
compared to Lambda-CDM. This property can be used to discriminate the model
from Lambda-CDM with current cosmological data.Comment: A few equations in the Appendix correcte
THE EFFECTIVENESS OF FISHBOWL METHOD ON STUDENTSâ SPEAKING SKILL AT THE SECOND GRADE STUDENTS OF SMA N 8 CIREBON
AYU WULANDARI. THE EFFECTIVENESS OF FISHBOWL METHOD ON
STUDENTSâ SPEAKING SKILL AT THE SECOND GRADE STUDENTS OF
SMA N 8 CIREBON
In Indonesia English has drawn up by government as foreign language that
the students should master English language. In fact, the students still have
weakness in skill of English, especially in speaking skill. In this thesis, the writer
focuses on the studentsâ speaking skill as Y variable that they have any weakness
to master speaking skill. And the writer focuses on the fishbowl method as the X
variable that will help student to practice speaking English.
The aims of this research are to find out the studentsâ responses towards the
application of fishbowl method, to find out the studentsâ achievement of speaking
skill before and after using the application of fishbowl method and to find out the
effectiveness of fishbowl method to improve the studentsâ speaking skill
Looking forward the problem in speaking skill that students have the
weakness in this skill thus the writer offered fishbowl method which can be
effective teaching tools for modeling group processes that can improve the
studentsâ speaking skill and more active in classroom to practice speaking
English.
The research design is quantitative research and experiment research. To
know the response the application of fishbowl method, the writer uses
questionnaire. To know the studentsâ achievement speaking skill, the writer uses
two tests, pretest and posttest. The data was analyzed statistically by using
Microsoft Excel, ANA test4 and SPSS program V 2.2.0.
The result of the studentsâ response towards the application of fishbowl
method is 1237 with the percentage 82,5 %, it can be categorized strong response.
And the result of the studentsâ achievement in speaking skill between
experimental class and control class where Gain of experiment class get the mean
score 0.26, but the N-Gain of control class get the mean score 0.12 so that the
deviation is 0.14. It means that the experiment class is better than control class in
improving the studentsâ speaking skill. Then conclusion of this thesis is that the
alternative hypothesis (Ha) is received and the Null Hypothesis (Ho) is refused
where t-test < t-table or <0.05. It means that there is any significant effectiveness
of using fishbowl method to improve studentsâ speaking skill the second grade
students of SMA N 8 Cirebon
The Vacuole Model: New Terms in the Second Order Deflection of Light
The present paper is an extension of a recent work (Bhattacharya et al. 2010)
to the Einstein-Strauss vacuole model with a cosmological constant, where we
work out the light deflection by considering perturbations up to order M^3 and
confirm the light bending obtained previously in their vacuole model by Ishak
et al. (2008). We also obtain another local coupling term
-((5{\pi}M^2{\Lambda})/8) related to {\Lambda}, in addition to the one obtained
by Sereno (2008, 2009). We argue that the vacuole method for light deflection
is exclusively suited to cases where the cosmological constant {\Lambda}
disappears from the path equation. However, the original Rindler-Ishak method
(2007) still applies even if a certain parameter {\gamma} of Weyl gravity does
not disappear. Here, using an alternative prescription, we obtain the known
term -(({\gamma}R)/2), as well as another new local term ((3{\pi}{\gamma}M)/2)
between M and {\gamma}. Physical implications are compared, where we argue that
the repulsive term -(({\gamma}R)/2) can be masked by the Schwarzschild term
((2M)/R) in the halo regime supporting attractive property of the dark matter.Comment: 15 page
Relational EPR
We study the EPR-type correlations from the perspective of the relational
interpretation of quantum mechanics. We argue that these correlations do not
entail any form of 'non-locality', when viewed in the context of this
interpretation. The abandonment of strict Einstein realism implied by the
relational stance permits to reconcile quantum mechanics, completeness,
(operationally defined) separability, and locality.Comment: Revised, published versio
Hidden symmetry of hyperbolic monopole motion
Hyperbolic monopole motion is studied for well separated monopoles. It is
shown that the motion of a hyperbolic monopole in the presence of one or more
fixed monopoles is equivalent to geodesic motion on a particular submanifold of
the full moduli space. The metric on this submanifold is found to be a
generalisation of the multi-centre Taub-NUT metric introduced by LeBrun. The
one centre case is analysed in detail as a special case of a class of systems
admitting a conserved Runge-Lenz vector. The two centre problem is also
considered. An integrable classical string motion is exhibited.Comment: 39 pages, 7 figures, references added, minor changes to section
Separation of the genetic loci for the H-Y antigen and for testis determination on human Y chromosome.
Foreground removal from WMAP 7yr polarization maps using an MLP neural network
One of the fundamental problems in extracting the cosmic microwave background
signal (CMB) from millimeter/submillimeter observations is the pollution by
emission from the Milky Way: synchrotron, free-free, and thermal dust emission.
To extract the fundamental cosmological parameters from CMB signal, it is
mandatory to minimize this pollution since it will create systematic errors in
the CMB power spectra. In previous investigations, it has been demonstrated
that the neural network method provide high quality CMB maps from temperature
data. Here the analysis is extended to polarization maps. As a concrete
example, the WMAP 7-year polarization data, the most reliable determination of
the polarization properties of the CMB, has been analysed. The analysis has
adopted the frequency maps, noise models, window functions and the foreground
models as provided by the WMAP Team, and no auxiliary data is included. Within
this framework it is demonstrated that the network can extract the CMB
polarization signal with no sign of pollution by the polarized foregrounds. The
errors in the derived polarization power spectra are improved compared to the
errors derived by the WMAP Team.Comment: Accepted for publication in Astrophysics & Space Scienc
Parity Mixed Doublets in A = 36 Nuclei
The -circular polarizations () and asymmetries
() of the parity forbidden M1 + E2 -decays: MeV) and MeV)
MeV) are investigated theoretically. We use the recently proposed
Warburton-Becker-Brown shell-model interaction. For the weak forces we discuss
comparatively different weak interaction models based on different assumptions
for evaluating the weak meson-hadron coupling constants. The results determine
a range of values from which we find the most probable values:
= for and = for .Comment: RevTeX, 17 pages; to appear in Phys. Rev.
Geometries with Killing Spinors and Supersymmetric AdS Solutions
The seven and nine dimensional geometries associated with certain classes of
supersymmetric and solutions of type IIB and D=11 supergravity,
respectively, have many similarities with Sasaki-Einstein geometry. We further
elucidate their properties and also generalise them to higher odd dimensions by
introducing a new class of complex geometries in dimensions, specified
by a Riemannian metric, a scalar field and a closed three-form, which admit a
particular kind of Killing spinor. In particular, for , we show that
when the geometry in dimensions is a cone we obtain a class of
geometries in dimensions, specified by a Riemannian metric, a scalar
field and a closed two-form, which includes the seven and nine-dimensional
geometries mentioned above when , respectively. We also consider various
ansatz for the geometries and construct infinite classes of explicit examples
for all .Comment: 28 page
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