210 research outputs found
On the Picard-Fuchs Equations of N=2 Supersymmetric E_6 Yang-Mills Theory
We obtain the Picard-Fuchs equations of N=2 supersymmetric Yang-Mills theory
with the exceptional gauge group E_6. Such equations are based on E_6 spectral
curve.Comment: Latex, 5 pages, few misprints are corrected, conclusion is adde
Spin Alignment of Dark Matter Halos: Mad Halos
We investigate the spin alignment of the dark matter halos by considering a
mechanism somewhat similar to tidal locking. We dubbed it Tidal Locking Theory
(TLT). While Tidal Torque Theory is responsible for the initial angular
momentum of the dark matter halos, the Tidal locking Theory explains the
angular momentum evolution during non-linear ages. Our previous work showed
that close encounters between haloes could drastically change their angular
momentum. The current manuscript argues that the tidal locking theory predicts
partial alignment between speed and the spin direction for the large high-speed
halos. To examine this prediction, we use the IllustrisTNG simulation and look
for the alignment of the halos' rotation axis. We find that the excess
probability of alignment between spin and speed is about 10 percent at
for fast haloes; with velocities larger than twice the median. We show that
tidal torque theory predicts that the spin of a halo tends to be aligned with
the middle eigendirection of the tidal tensor. Moreover, we find that the halos
at are preferentially aligned with the middle eigendirection of the
tidal tensor with an excess probability of 15 percent. We show that tidal
torque theory fails to predict correct alignment at while it works almost
flawlessly at .Comment: 7 pages, 4 figure
Local Features with Large Spiky non-Gaussianities during Inflation
We provide a dynamical mechanism to generate localized features during
inflation. The local feature is due to a sharp waterfall phase transition which
is coupled to the inflaton field. The key effect is the contributions of
waterfall quantum fluctuations which induce a sharp peak on the curvature
perturbation which can be as large as the background curvature perturbation
from inflaton field. Due to non-Gaussian nature of waterfall quantum
fluctuations a large spike non-Gaussianity is produced which is narrowly peaked
at modes which leave the Hubble radius at the time of phase transition. The
large localized peaks in power spectrum and bispectrum can have interesting
consequences on CMB anisotropies.Comment: 22 pages, 2 figure
Effects of Variable Newton Constant During Inflation
In this paper the effects of time-dependent Newton constant G during
inflation are studied. We present the formalism of curvature perturbations in
an inflationary system with a time-dependent Newton constant. As an example we
consider a toy model in which G undergoes a sudden change during inflation. By
imposing the appropriate matching conditions the imprints of this sharp change
in G on curvature perturbation power spectrum are studied. We show that if G
increases (decreases) during the transition the amplitude of curvature
perturbations on large scales decreases (increases). In our model with a sudden
change in G a continuous sinusoidal modulations on curvature power spectrum is
induced. However, in a realistic scenario in which the change in G has some
finite time scale we expect these sinusoidal modulations to be damped on short
scales. The generated features may be used to explain the observed glitches on
CMB power spectrum. This puts a bound on during inflation of roughly
the same order as current bounds on during the entire observed age
of the universe.Comment: 15 pages, 2 figures. Typos fixed, new references added, conforms with
the journal versio
The Importance of Slow-roll Corrections During Multi-field Inflation
We re-examine the importance of slow-roll corrections during the evolution of
cosmological perturbations in models of multi-field inflation. We find that in
many instances the presence of light degrees of freedom leads to situations in
which next to leading order slow-roll corrections become significant. Examples
where we expect such corrections to be crucial include models in which modes
exit the Hubble radius while the inflationary trajectory undergoes an abrupt
turn in field space, or during a phase transition. We illustrate this with two
examples -- hybrid inflation and double quadratic inflation. Utilizing both
analytic estimates and full numerical results, we find that corrections can be
as large as 20%. Our results have implications for many existing models in the
literature, as these corrections must be included to obtain accurate
observational predictions -- particularly given the level of accuracy expected
from CMB experiments such as PlanckComment: v1: 21 pages, 3 figures, 1 appendix. v2: clarifications to
{\S}{\S}2.1, 3.1 and 4, {\S}5.3 added, references added, results unchanged.
Matches published version in JCA
Issues on Generating Primordial Anisotropies at the End of Inflation
We revisit the idea of generating primordial anisotropies at the end of
inflation in models of inflation with gauge fields. To be specific we consider
the charged hybrid inflation model where the waterfall field is charged under a
U(1) gauge field so the surface of end of inflation is controlled both by
inflaton and the gauge fields. Using delta N formalism properly we find that
the anisotropies generated at the end of inflation from the gauge field
fluctuations are exponentially suppressed on cosmological scales. This is
because the gauge field evolves exponentially during inflation while in order
to generate appreciable anisotropies at the end of inflation the spectator
gauge field has to be frozen and scale invariant. We argue that this is a
generic feature, that is, one can not generate observable anisotropies at the
end of inflation within an FRW background.Comment: V3: new references added, JCAP published versio
Large-scale Perturbations from the Waterfall Field in Hybrid Inflation
We estimate large-scale curvature perturbations from isocurvature
fluctuations in the waterfall field during hybrid inflation, in addition to the
usual inflaton field perturbations. The tachyonic instability at the end of
inflation leads to an explosive growth of super-Hubble scale perturbations, but
they retain the steep blue spectrum characteristic of vacuum fluctuations in a
massive field during inflation. The power spectrum thus peaks around the
Hubble-horizon scale at the end of inflation. We extend the usual delta-N
formalism to include the essential role of these small fluctuations when
estimating the large-scale curvature perturbation. The resulting curvature
perturbation due to fluctuations in the waterfall field is second-order and the
spectrum is expected to be of order 10^{-54} on cosmological scales.Comment: 10 pages, 4 figures; v2 comments added on application of delta-N
formalism including Hubble scale fluctuation
Rehydration of air-dried cervical smears: An alternative to routine wet fixation
To prepare Pap smears, the routine practice is to fix the slides immediately in 95 ethanol. This study was performed to evaluate the possibility of routine use of alternative method of air-drying and rehydration prior to alcohol fixation instead of conventional method. Paired cervical smears with at least low cellularity were collected from 117 women who participated in the study. One set was labeled WF (wet fixed or fixed immediately in 95 ethanol) and the other one ARF (air-dried, rehydrated and fixed). The latter further split into 3 subgroups based on the duration of air-drying. The staining quality of the slides was assessed with respect to chromatin, nuclear and cytoplasmic borders, cytolysis, cellularity, cytoplasmic staining, and red blood cells lysis. Then they were graded blindly. The results were analyzed by Chi square test to compare the defined parameters between the 2 groups and also the 3 subgroups. ARF slides were significantly better with regard to clearance of background due to the lysis of red blood cells (P value, 0.000, x2 test; kappa, -0.27). No statistically significant differences were noted between two groups in terms of other cytologic features. Cytologic features of ARF slides were statistically identical to WF smears. However, red blood cells lysis rendered clearer background in ARF slides. Air-drying and rehydration of slides is a superior method for heavily blood stained smears and can be used at least with identical quality for routine practice. © 2007 Tehran University of Medical Sciences. All rights reserved
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