603 research outputs found
The Real Combination Problem : Panpsychism, Micro-Subjects, and Emergence
Panpsychism harbors an unresolved tension, the seriousness of which has yet to be fully appreciated. I capture this tension as a dilemma, and offer panpsychists advice on how to resolve it. The dilemma, briefly, is as follows. Panpsychists are committed to the perspicuous explanation of macro-mentality in terms of micro-mentality. But panpsychists take the micro-material realm to feature not just mental properties, but also micro-subjects to whom these properties belong. Yet it is impossible to explain the constitution of a macro-subject (like one of us) in terms of the assembly of micro-subjects, for, I show, subjects cannot combine. Therefore the panpsychist explanatory project is derailed by the insistence that the world’s ultimate material constituents (ultimates) are subjects of experience. The panpsychist faces a choice of abandoning her explanatory project, or recanting the claim that the ultimates are subjects. This is the dilemma. I argue that the latter option is to be preferred. This needn’t constitute a wholesale abandonment of panpsychism, however, since panpsychists can maintain that the ultimates possess phenomenal qualities, despite not being subjects of those qualities. This proposal requires us to make sense of phenomenal qualities existing independently of experiencing subjects, a challenge I tackle in the penultimate section. The position eventually reached is a form of neutral monism, so another way to express the overall argument is to say that, keeping true to their philosophical motivations, panpsychists should really be neutral monists.Peer reviewedFinal Accepted Versio
Reconnection of Non-Abelian Cosmic Strings
Cosmic strings in non-abelian gauge theories naturally gain a spectrum of
massless, or light, excitations arising from their embedding in color and
flavor space. This opens up the possibility that colliding strings miss each
other in the internal space, reducing the probability of reconnection. We study
the topology of the non-abelian vortex moduli space to determine the outcome of
string collision. Surprisingly we find that the probability of classical
reconnection in this system remains unity, with strings passing through each
other only for finely tuned initial conditions. We proceed to show how this
conclusion can be changed by symmetry breaking effects, or by quantum effects
associated to fermionic zero modes, and present examples where the probability
of reconnection in a U(N) gauge theory ranges from 1/N for low-energy
collisions to one at higher energies.Comment: 25 Pages, 3 Figures. v2: comment added, reference adde
Stochastic Inflation Revisited: Non-Slow Roll Statistics and DBI Inflation
Stochastic inflation describes the global structure of the inflationary
universe by modeling the super-Hubble dynamics as a system of matter fields
coupled to gravity where the sub-Hubble field fluctuations induce a stochastic
force into the equations of motion. The super-Hubble dynamics are ultralocal,
allowing us to neglect spatial derivatives and treat each Hubble patch as a
separate universe. This provides a natural framework in which to discuss
probabilities on the space of solutions and initial conditions. In this article
we derive an evolution equation for this probability for an arbitrary class of
matter systems, including DBI and k-inflationary models, and discover
equilibrium solutions that satisfy detailed balance. Our results are more
general than those derived assuming slow roll or a quasi-de Sitter geometry,
and so are directly applicable to models that do not satisfy the usual slow
roll conditions. We discuss in general terms the conditions for eternal
inflation to set in, and we give explicit numerical solutions of highly
stochastic, quasi-stationary trajectories in the relativistic DBI regime.
Finally, we show that the probability for stochastic/thermal tunneling can be
significantly enhanced relative to the Hawking-Moss instanton result due to
relativistic DBI effects.Comment: 38 pages, 2 figures. v3: minor revisions; version accepted into JCA
Wall and Anti-Wall in the Randall-Sundrum Model and A New Infrared Regularization
An approach to find the field equation solution of the Randall-Sundrum model
with the extra axis is presented. We closely examine the infrared
singularity. The vacuum is set by the 5 dimensional Higgs field. Both the
domain-wall and the anti-domain-wall naturally appear, at the {\it ends} of the
extra compact axis, by taking a {\it new infrared regularization}. The
stability is guaranteed from the outset by the kink boundary condition. A {\it
continuous} (infrared-)regularized solution, which is a truncated {\it Fourier
series} of a {\it discontinuous} solution, is utilized.The ultraviolet-infrared
relation appears in the regularized solution.Comment: 36 pages, 29 eps figure file
Outflow Facility Effects of 3 Schlemm’s Canal Microinvasive Glaucoma Surgery Devices
Purpose
To study the effect of 3 Schlemm’s canal (SC) microinvasive glaucoma surgery (MIGS) devices on outflow facility.
Design
Paired comparisons, randomized design, baseline-controlled study.
Participants
Thirty-six pairs of dissected anterior segments from donated human eye bank eyes without glaucoma were studied. A baseline measurement was collected from each eye to serve as its control.
Methods
Using a constant pressure perfusion method, outflow facility was measured in paired eyes from human donors. Measurements were made at perfusion pressures of 10 mmHg, 20 mmHg, 30 mmHg, and 40 mmHg. Outflow facility was measured before (baseline control) and after the implantation of an SC glaucoma drainage device or sham procedure. Three sets of experiments were carried out comparing 1 and 2 iStent Trabecular Micro-Bypass Stents and 2 iStent Inject implants with the Hydrus Microstent.
Main Outcome Measures
Change in outflow facility from baseline or contralateral eye.
Results
After Hydrus placement, the outflow facility increased from 0.23±0.03 μl/minute per millimeter of mercury at baseline to 0.38±0.03 μl/minute per millimeter of mercury (P < 0.001). The percent increase in outflow facility was 79±21% for the Hydrus and 11±16% for the 2 iStent Inject devices, a difference that was significant (P = 0.018). Outflow facility with 1 iStent (0.38±0.07 μl/minute per millimeter of mercury) was greater than baseline (0.28±0.03 μl/minute per millimeter of mercury; P = 0.031). The 1 iStent showed a greater increase in outflow facility from baseline (0.10±0.04 μl/minute per millimeter of mercury) compared with the sham procedure (–0.08±0.05 μl/minute per millimeter of mercury; P = 0.042). No other significant differences were found.
Conclusions
The longer the MIGS device, and thus the more SC that it dilates, the greater the outflow facility
Tunneling and propagation of vacuum bubbles on dynamical backgrounds
In the context of bubble universes produced by a first-order phase transition
with large nucleation rates compared to the inverse dynamical time scale of the
parent bubble, we extend the usual analysis to non-vacuum backgrounds. In
particular, we provide semi-analytic and numerical results for the modified
nucleation rate in FLRW backgrounds, as well as a parameter study of bubble
walls propagating into inhomogeneous (LTB) or FLRW spacetimes, both in the
thin-wall approximation. We show that in our model, matter in the background
often prevents bubbles from successful expansion and forces them to collapse.
For cases where they do expand, we give arguments why the effects on the
interior spacetime are small for a wide range of reasonable parameters and
discuss the limitations of the employed approximations.Comment: 29 pages, 8 figures, typos corrected, matches published versio
The vacuum bubbles in de Sitter background and black hole pair creation
We study the possible types of the nucleation of vacuum bubbles. We classify
vacuum bubbles in de Sitter background and present some numerical solutions.
The thin-wall approximation is employed to obtain the nucleation rate and the
radius of vacuum bubbles. With careful analysis we confirm that Parke's formula
is also applicable to the large true vacuum bubbles. The nucleation of the
false vacuum bubble in de Sitter background is also evaluated. The tunneling
process in the potential with degenerate vacua is analyzed as the limiting
cases of the large true vacuum bubble and false vacuum bubble. Next, we
consider the pair creation of black holes in the background of bubble
solutions. We obtain static bubble wall solutions of junction equation with
black hole pair. The masses of created black holes are uniquely determined by
the cosmological constant and surface tension on the wall. Finally, we obtain
the rate of pair creation of black holes.Comment: 3 figures, minor including errors and typos corrected, and refs.
adde
A geometric description of the non-Gaussianity generated at the end of multi-field inflation
In this paper we mainly focus on the curvature perturbation generated at the
end of multi-field inflation, such as the multi-brid inflation. Since the
curvature perturbation is produced on the super-horizon scale, the bispectrum
and trispectrum have a local shape. The size of bispectrum is measured by
and the trispectrum is characterized by two parameters and
. For simplicity, the trajectory of inflaton is assumed to be a
straight line in the field space and then the entropic perturbations do not
contribute to the curvature perturbation during inflation. As long as the
background inflaton path is not orthogonal to the hyper-surface for inflation
to end, the entropic perturbation can make a contribution to the curvature
perturbation at the end of inflation and a large local-type non-Gaussiantiy is
expected. An interesting thing is that the non-Gaussianity parameters are
completely determined by the geometric properties of the hyper-surface of the
end of inflation. For example, is proportional to the curvature of the
curve on this hyper-surface along the adiabatic direction and is
related to the change of the curvature radius per unit arc-length of this
curve. Both and can be positive or negative respectively, but
must be positive and not less than .Comment: 19 pages, 4 figures; refs added; a correction to \tau_{NL} for
n-field inflation added, version accepted for publication in JCA
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