5,895 research outputs found
Asymmetrical bloch branes and the hierarchy problem
We investigate a two scalar fields split braneworld model which leads to a
possible approach to the hierarchy problem within the thick brane scenario. The
model exhibits a resulting asymmetric warp factor suitable for this purpose.
The solution is obtained by means of the orbit equation approach for a specific
value of one of the parameters. Besides, we analyze the model qualitative
behaviour for arbitrary parameters by inspecting the underlying dynamical
system defined by the equations which give rise to the braneworld model. We
finalize commenting on the metric fluctuation and stability issues.Comment: 8 pages, 7 figure
Five-Dimensional f(R) Braneworld Models
After incorporating the f(R) gravity into the general braneworld sum rules
scope, it is shown that some particular class of warped five dimensional
nonlinear braneworld models, which may be interesting for the hierarchy problem
solution, still require a negative tension brane. For other classes of warp
factors (suitable and not suitable for approaching the hierarchy problem) it is
not necessary any negative brane tension in the compactification scheme. In
this vein, it is argued that in the bulk f(R) gravity context, some types of
warp factors may be useful for approaching the hierarchy problem and for
evading the necessity of a negative brane tension in the compactification
scheme.Comment: 10 pages, references updated, small modifications. Accepted for
publication in Phys. Rev.
Late Holocene climate and environmental changes in Kamchatka inferred from subfossil chironomid record.
This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid
remains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-Yurts
Lake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomid
head capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini,
Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid
assemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 and
4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake water
conditions and close to modern temperatures (w13 �C). From 4000 to 1000 cal years BP, two consecutive
warm intervals were recorded, with the highest reconstructed temperature reaching 16.8 �C between
3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperatures
during the last stage of the Holocene. Comparison with other regional studies has shown that termination
of cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, South
Kurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP to
the last millennium, a newly strengthened climate continentality accompanied by general warming
trend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region.
Some timing differences in climatic changes reconstructed from chironomid record of TYL sediments and
late Holocene events reconstructed from other sites and other proxies might be linked to differences in
local forcing mechanisms or caused by the different degree of dating precision, the different temporal
resolution, and the different sensitive responses of climate proxies to the climate variations. Further
high-resolution stratigraphic studies in this region are needed to understand the spatially complex
pattern of climate change in Holocene in Kamchatka and the surrounding region.
14N and 15N coupling constants of the oxidized primary donor P-860 of bacterial photosynthesis obtained by electron spin echo envelope modulation spectroscopy
An electron spin echo modulation frequency analysis of P+-860 is performed in 14N chromatophores of Rhodospirillum rubrum, and in 15N substituted reaction centers from Rhodopseudomonas sphaeroides 2.4.1. For the 14N material two sets of nuclear quadrupole parameters are obtained. From the frequencies found for 15N reaction centers the perpendicular, parallel and isotropic hyperfine previous termcouplingnext term constants of three of the four bacteriochlorophyll nitrogen nuclei are inferred
Searching for Elko dark matter spinors at the CERN LHC
The aim of this work is to explore the possibility to discover a fermionic
field with mass dimension one, the Elko field, in the Large Hadron Collider
(LHC). Due to its mass dimension, an Elko can only interact either with
Standard Model (SM) spinors and gauge fields at 1-loop order or at tree level
through a quartic interaction with the Higgs field. In this Higgs portal
scenario, the Elko is a viable candidate to a dark matter constituent which has
been shown to be compatible with relic abundance measurements from WMAP and
direct dark matter--nucleon searches. We propose a search strategy for this
dark matter candidate in the channel at
the TeV LHC. We show the LHC potential to discover the Elko
considering a triple Higgs-Elko coupling as small as after 1
pb of integrated luminosity. Some phenomenological consequences of this
new particle and its collider signatures are also discussed.Comment: 7 pages, 3 figure
Constraining Elko Dark Matter at the LHC with Monophoton Events
A mass dimension one fermion, also known as Elko, constitutes a dark matter
candidate which might interact with photons at the tree level in a specific
fashion. In this work, we investigate the constraints imposed by unitarity and
LHC data on this type of interactions using the search for new physics in
monophoton events. We found that Elkos which can explain the dark matter relic
abundance mainly through electromagnetic interactions are excluded at the
95\%CL by the 8 TeV LHC data for masses up to 1 TeV.Comment: 6 pages, 4 figure
Searching for pathways involving dressed states in optimal control theory
Selective population of dressed states has been proposed as an alternative control
pathway in molecular reaction dynamics [Wollenhaupt et al., J. Photochem.
Photobiol. A: Chem., 2006, 180, 248]. In this article we investigate if, and under
which conditions, this strong field pathway is included in the search space of
optimal control theory. For our calculations we used the proposed example of the
potassium dimer, in which the different target states can be reached via dressed
states by resonant transition. Especially, we investigate whether the optimization
algorithm is able to find the route involving the dressed states although the target
state lies out of resonance in the bare state picture
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