24 research outputs found
Sphalerons and the Electroweak Phase Transition in Models with Higher Scalar Representations
In this work we investigate the sphaleron solution in a
gauge theory, which also encompasses the Standard Model, with higher scalar
representation(s) (). We show that the field profiles
describing the sphaleron in higher scalar multiplet, have similar trends like
the doublet case with respect to the radial distance. We compute the sphaleron
energy and find that it scales linearly with the vacuum expectation value of
the scalar field and its slope depends on the representation. We also
investigate the effect of gauge field and find that it is small for the
physical value of the mixing angle, and resembles the case for the
doublet. For higher representations, we show that the criterion for strong
first order phase transition, , is relaxed with respect to
the doublet case, i.e. .Comment: 20 pages, 5 figures & 1 table, published versio
Skyrmion Multi-Walls
Skyrmion walls are topologically-nontrivial solutions of the Skyrme system
which are periodic in two spatial directions. We report numerical
investigations which show that solutions representing parallel multi-walls
exist. The most stable configuration is that of the square -wall, which in
the limit becomes the cubically-symmetric Skyrme crystal. There is
also a solution resembling parallel hexagonal walls, but this is less stable.Comment: 7 pages, 1 figur
MSSM Baryogenesis and Electric Dipole Moments: An Update on the Phenomenology
We explore the implications of electroweak baryogenesis for future searches
for permanent electric dipole moments in the context of the minimal
supersymmetric extension of the Standard Model (MSSM). From a cosmological
standpoint, we point out that regions of parameter space that over-produce
relic lightest supersymmetric particles can be salvaged only by assuming a
dilution of the particle relic density that makes it compatible with the dark
matter density: this dilution must occur after dark matter freeze-out, which
ordinarily takes place after electroweak baryogenesis, implying the same degree
of dilution for the generated baryon number density as well. We expand on
previous studies on the viable MSSM regions for baryogenesis, exploring for the
first time an orthogonal slice of the relevant parameter space, namely the
(tan\beta, m_A) plane, and the case of non-universal relative gaugino-higgsino
CP violating phases. The main result of our study is that in all cases lower
limits on the size of the electric dipole moments exist, and are typically on
the same order, or above, the expected sensitivity of the next generation of
experimental searches, implying that MSSM electroweak baryogenesis will be soon
conclusively tested.Comment: 23 pages, 10 figures, matches version published in JHE
Estimating Black Hole Masses in Quasars Using Broad Optical and UV Emission Lines
We review past work using broad emission lines as virial estimators of black
hole masses in quasars. Basically one requires estimates of the emitting region
radius and virial velocity dispersion to obtain black hole masses. The three
major ways to estimate the broad-line emitting region (BLR) radius involve: (1)
direct reverberation mapping, (2) derivation of BLR radius for larger samples
using the radius-luminosity correlation derived from reverberation measures,
and (3) estimates of BLR radius using the definition of the ionization
parameter solved for BLR radius (photoionization method). At low redshift (z <
0.7) FWHM H-beta serves as the most widely used estimator of virial velocity
dispersion. FWHM H-beta can provide estimates for tens of thousands of quasars
out to z ~ 3.8 (IR spectroscopy beyond z ~ 1). A new photoionization method
also shows promise for providing many reasonable estimates of BLR radius via
high S/N IR spectroscopy of the UV region 1300 -- 2000 A. FWHM MgII 2800 can
serve as a surrogate for FWHM H-beta in the range 0.4 < z < 6.5 while CIV 1549
is affected by broadening due to non-virial motions and best avoided (i.e.
there is no clear conversion factor between FWHM H-beta and FWHM CIV 1549).
Most quasars yield black hole mass estimates in the range 7 < log M< 9.7. There
is no strong evidence for values above 10.0 and there may be evidence for a
turnover in the maximum black hole mass near z ~ 5.Comment: Accepted for publication in New Astronomy Reviews. The work was
presented as an invited talk at special workshop "Spectral lines and
super-massive black holes" held on June 10, 2011 as a part of activity in the
frame of COST action 0905 "Black holes in an violent universe" and as a part
of the 8th Serbian Conference on Spectral Line Shapes in Astrophysic