271 research outputs found
Superweakly interacting dark matter from the Minimal Walking Technicolor
We study a superweakly interacting dark matter particle motivated by minimal
walking technicolor theories. Our WIMP is a mixture of a sterile state and a
state with the charges of a standard model fourth family neutrino. We show that
the model can give the right amount of dark matter over a range of the WIMP
mass and mixing angle. We compute bounds on the model parameters from the
current accelerator data including the oblique corrections to the precision
electroweak parameters, as well as from cryogenic experiments, Super-Kamiokande
and from the IceCube experiment. We show that consistent dark matter solutions
exist which satisfy all current constraints. However, almost the entire
parameter range of the model lies within the the combined reach of the next
generation experiments.Comment: 29 pages, 6 figure
Comparative performance of selected variability detection techniques in photometric time series
Photometric measurements are prone to systematic errors presenting a
challenge to low-amplitude variability detection. In search for a
general-purpose variability detection technique able to recover a broad range
of variability types including currently unknown ones, we test 18 statistical
characteristics quantifying scatter and/or correlation between brightness
measurements. We compare their performance in identifying variable objects in
seven time series data sets obtained with telescopes ranging in size from a
telephoto lens to 1m-class and probing variability on time-scales from minutes
to decades. The test data sets together include lightcurves of 127539 objects,
among them 1251 variable stars of various types and represent a range of
observing conditions often found in ground-based variability surveys. The real
data are complemented by simulations. We propose a combination of two indices
that together recover a broad range of variability types from photometric data
characterized by a wide variety of sampling patterns, photometric accuracies,
and percentages of outlier measurements. The first index is the interquartile
range (IQR) of magnitude measurements, sensitive to variability irrespective of
a time-scale and resistant to outliers. It can be complemented by the ratio of
the lightcurve variance to the mean square successive difference, 1/h, which is
efficient in detecting variability on time-scales longer than the typical time
interval between observations. Variable objects have larger 1/h and/or IQR
values than non-variable objects of similar brightness. Another approach to
variability detection is to combine many variability indices using principal
component analysis. We present 124 previously unknown variable stars found in
the test data.Comment: 29 pages, 8 figures, 7 tables; accepted to MNRAS; for additional
plots, see http://scan.sai.msu.ru/~kirx/var_idx_paper
Introduction to Magnetic Monopoles
One of the most basic properties of magnetism is that a magnet always has two
poles, north and south, which cannot be separated into isolated poles, i.e.,
magnetic monopoles. However, there are strong theoretical arguments why
magnetic monopoles should exist. In spite of extensive searches they have not
been found, but they have nevertheless played a central role in our
understanding of physics at the most fundamental level.Comment: 22 pages, 7 figures. To be published in Contemporary Physic
V371 Per - A Thick-Disk, Short-Period F/1O Cepheid
V371 Per was found to be a double-mode Cepheid with a fundamental mode period
of 1.738 days, the shortest among Galactic beat Cepheids, and an unusually high
period ratio of 0.731, while the other Galactic beat Cepheids have period
ratios between 0.697 and 0.713. The latter suggests that the star has a
metallicity [Fe/H] between -1 and -0.7. The derived distance from the Galactic
Plane places it in the Thick Disk or the Halo, while all other Galactic beat
Cepheids belong to the Thin Disk. There are indications from historical data
that both the fundamental and first overtone periods have lengthened.Comment: Accepted for publication in MNRA
Search for anomalous top-gluon couplings at LHC revisited
Through top-quark pair productions at LHC, we study possible effects of
nonstandard top-gluon couplings yielded by SU(3)xSU(2)xU(1) invariant
dimension-6 effective operators. We calculate the total cross section and also
some distributions for p p -> t tbar X as functions of two anomalous-coupling
parameters, i.e., the chromoelectric and chromomagnetic moments of the top,
which are constrained by the total cross section sigma(p pbar -> t tbar X)
measured at Tevatron. We find that LHC might give us some chances to observe
sizable effects induced by those new couplings.Comment: One comment and related two refs. added. Final version (to appear in
Eur.Phys.J. C
In-the-Gap SU UMa-Type Dwarf Nova, Var73 Dra with a Supercycle of about 60 Days
An intensive photometric-observation campaign of the recently discovered SU
UMa-type dwarf nova, Var73 Dra was conducted from 2002 August to 2003 February.
We caught three superoutbursts in 2002 October, December and 2003 February. The
recurrence cycle of the superoutburst (supercycle) is indicated to be 60
d, the shortest among the values known so far in SU UMa stars and close to
those of ER UMa stars. The superhump periods measured during the first two
superoutbursts were 0.104885(93) d, and 0.10623(16) d, respectively. A
0.10424(3)-d periodicity was detected in quiescence. The change rate of the
superhump period during the second superoutburst was , which
is an order of magnitude larger than the largest value ever known. Outburst
activity has changed from a phase of frequent normal outbursts and infrequent
superoutbursts in 2001 to a phase of infrequent normal outbursts and frequent
superoutbursts in 2002. Our observations are negative to an idea that this star
is an related object to ER UMa stars in terms of the duty cycle of the
superoutburst and the recurrence cycle of the normal outburst. However, to
trace the superhump evolution throughout a superoutburst, and from quiescence
more effectively, may give a fruitful result on this matter.Comment: 9 pages, 8 figures, submitted to A&
Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates
© 2018 Burilov et al. The synthesis of new calix[4]arenes adopting a cone stereoisomeric form bearing two or four azide fragments on the upper rim and water-soluble triazolyl amphiphilic receptors with two or four polyammonium headgroups via copper-catalyzed azide–alkyne cycloaddition reaction has been performed for the first time. It was found that the synthesized macrocycles form stable aggregates with hydrodynamic diameters between 150–200 nm and electrokinetic potentials about +40 to +60 mV in water solutions. Critical aggregation concentration (CAC) values were measured using a micelle method with pyrene and eosin Y as dye probes. The CAC values of tetraalkyl-substituted macrocycles 12a,b (5 µM for both) are significantly lower than those for dialkyl-substituted macrocycles 10a,b (790 and 160 µM, respectively). Premicellar aggregates of macrocycles 10a,b and 12a,b with the dye eosin Y were used for nucleotides sensing through a dye replacement procedure. It is unusual that disubstituted macrocycles 10a,b bind more effectively a less charged adenosine 5'-diphosphate (ADP) than adenosine 5'-triphosphate (ATP). A simple colorimetric method based on polydiacetylene vesicles decorated with 10b was elaborated for the naked-eye detection of ADP with a detection limit of 0.5 mM
Stirring Strongly Coupled Plasma
We determine the energy it takes to move a test quark along a circle of
radius L with angular frequency w through the strongly coupled plasma of N=4
supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w
the energy deposited by stirring the plasma in this way is governed either by
the drag force acting on a test quark moving through the plasma in a straight
line with speed v=Lw or by the energy radiated by a quark in circular motion in
the absence of any plasma, whichever is larger. There is a continuous crossover
from the drag-dominated regime to the radiation-dominated regime. In the
crossover regime we find evidence for significant destructive interference
between energy loss due to drag and that due to radiation as if in vacuum. The
rotating quark thus serves as a model system in which the relative strength of,
and interplay between, two different mechanisms of parton energy loss is
accessible via a controlled classical gravity calculation. We close by
speculating on the implications of our results for a quark that is moving
through the plasma in a straight line while decelerating, although in this case
the classical calculation breaks down at the same value of the deceleration at
which the radiation-dominated regime sets in.Comment: 27 pages LaTex, 5 figure
Higgs production as a probe of anomalous top couplings
The LHC may be currently seeing the first hints of the Higgs boson. The
dominant production mode for the Higgs at the LHC involves a top-quark loop. An
accurate measurement of Higgs production cross-sections and decay widths can
thus be used to obtain limits on anomalous top couplings. We find that such an
exercise could potentially yield constraints that are stronger than those
derived from low-energy observables as well as direct bounds expected from the
top pair-production process.Comment: Version published in JHE
Asymptotic safety guaranteed
We study the ultraviolet behaviour of four-dimensional quantum field theories involving non-abelian gauge fields, fermions and scalars in the Veneziano limit. In a regime where asymptotic freedom is lost, we explain how the three types of fields cooperate to develop fully interacting ultraviolet fixed points, strictly controlled by perturbation theory. Extensions towards strong coupling and beyond the large-N limit are discussed
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