4,614 research outputs found
Investigation into the site and mode of antivertigo action of a new phenothiazine derivative Final report
Cerebellum site and mode of antivertigo action of thiethylperazin
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The road less travelled: Gender identity discrimination in the US and UK
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What can the observation of nonzero curvature tell us?
The eternally inflating multiverse provides a consistent framework to
understand coincidences and fine-tuning in the universe. As such, it provides
the possibility of finding another coincidence: if the amount of slow-roll
inflation was only slightly more than the anthropic threshold, then spatial
curvature might be measurable. We study this issue in detail, particularly
focusing on the question: "If future observations reveal nonzero curvature,
what can we conclude?" We find that whether an observable signal arises or not
depends crucially on three issues: the cosmic history just before the
observable inflation, the measure adopted to define probabilities, and the
nature of the correlation between the tunneling and slow-roll parts of the
potential. We find that if future measurements find positive curvature at
\Omega_k < -10^-4, then the framework of the eternally inflating multiverse is
excluded with high significance. If the measurements instead reveal negative
curvature at \Omega_k > 10^-4, then we can conclude (1) diffusive (new or
chaotic) eternal inflation did not occur in our immediate past; (2) our
universe was born by a bubble nucleation; (3) the probability measure does not
reward volume increase; and (4) the origin of the observed slow-roll inflation
is an accidental feature of the potential, not due to a theoretical mechanism.
Discovery of \Omega_k > 10^-4 would also give us nontrivial information about
the correlation between tunneling and slow-roll; e.g. a strong correlation
favoring large N would be excluded in certain measures. We also ask whether the
current constraint on \Omega_k is consistent with multiverse expectations,
finding that the answer is yes, except for certain cases. In the course of this
work we were led to consider vacuum decay branching ratios, and found that it
is more likely than one might guess that the decays are dominated by a single
channel.Comment: 46 pages, 5 figures; reference updates and typo corrections arising
from final Phys. Rev. D copy editin
Domain Walls in SU(5)
We consider the Grand Unified SU(5) model with a small or vanishing cubic
term in the adjoint scalar field in the potential. This gives the model an
approximate or exact Z symmetry whose breaking leads to domain walls. The
simplest domain wall has the structure of a kink across which the Higgs field
changes sign () and inside which the full SU(5) is restored.
The kink is shown to be perturbatively unstable for all parameters. We then
construct a domain wall solution that is lighter than the kink and show it to
be perturbatively stable for a range of parameters. The symmetry in the core of
this domain wall is smaller than that outside. The interactions of the domain
wall with magnetic monopole is discussed and it is shown that magnetic
monopoles with certain internal space orientations relative to the wall pass
through the domain wall. Magnetic monopoles in other relative internal space
orientations are likely to be swept away on collision with the domain walls,
suggesting a scenario where the domain walls might act like optical
polarization filters, allowing certain monopole ``polarizations'' to pass
through but not others. As SU(5) domain walls will also be formed at small
values of the cubic coupling, this leads to a very complicated picture of the
evolution of defects after the Grand Unified phase transition.Comment: 6 pages, 1 figure. Animations can be viewed at
http://theory4.phys.cwru.edu/~levon/figures.htm
Scenario of inflationary cosmology from the phenomenological models
Choosing the three phenomenological models of the dynamical cosmological term
, viz., , and
where is the cosmic scale factor, it has been shown by
the method of numerical analysis that the three models are equivalent for the
flat Universe . The evolution plots for dynamical cosmological term
vs. time and also the cosmic scale factor vs. are drawn
here for . A qualitative analysis has been made from the plots which
supports the idea of inflation and hence expanding Universe.Comment: 12 latex pages with 12 figures; Replaced with the revised version;
Accepeted for `J. Non-lin. Frac. Phen. Sci. Engg.
Non-topological solitons as nucleation sites for cosmological phase transitions
I consider quantum field theories that admit charged non-topological solitons
of the Q-ball type, and use the fact that in a first-order cosmological phase
transition, below the critical temperature, there is a value of the soliton
charge above which the soliton becomes unstable and expands, converting space
to the true vacuum, much like a critical bubble in the case of ordinary
tunneling. Using a simple model for the production rate of Q-balls through
charge accretion during a random walk out of equilibrium, I calculate the
probability for the formation of critical charge solitons and estimate the
amount of supercooling needed for the phase transition to be completed.Comment: 20 pages, 2 figures, some comments and references adde
Monopole Vector Spherical Harmonics
Eigenfunctions of total angular momentum for a charged vector field
interacting with a magnetic monopole are constructed and their properties
studied. In general, these eigenfunctions can be obtained by applying vector
operators to the monopole spherical harmonics in a manner similar to that often
used for the construction of the ordinary vector spherical harmonics. This
construction fails for the harmonics with the minimum allowed angular momentum.
These latter form a set of vector fields with vanishing covariant curl and
covariant divergence, whose number can be determined by an index theorem.Comment: 21 pages, CU-TP-60
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