1,545 research outputs found
Modulus Stabilization with Bulk Fields
We propose a mechanism for stabilizing the size of the extra dimension in the
Randall-Sundrum scenario. The potential for the modulus field that sets the
size of the fifth dimension is generated by a bulk scalar with quartic
interactions localized on the two 3-branes. The minimum of this potential
yields a compactification scale that solves the hierarchy problem without fine
tuning of parameters.Comment: 8 pages, LaTeX; minor typo correcte
Anthropic Distribution for Cosmological Constant and Primordial Density Perturbations
The anthropic principle has been proposed as an explanation for the observed
value of the cosmological constant. Here we revisit this proposal by allowing
for variation between universes in the amplitude of the scale-invariant
primordial cosmological density perturbations. We derive a priori probability
distributions for this amplitude from toy inflationary models in which the
parameter of the inflaton potential is smoothly distributed over possible
universes. We find that for such probability distributions, the likelihood that
we live in a typical, anthropically-allowed universe is generally quite small.Comment: 12 pages, 2 tables. v3: Replaced to match published version (minor
corrections of form
Activated lymphocyte recruitment into the tumor microenvironment following preoperative sipuleucel-T for localized prostate cancer.
BackgroundSipuleucel-T is a US Food and Drug Administration-approved immunotherapy for asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). Its mechanism of action is not fully understood. This prospective trial evaluated the direct immune effects of systemically administered sipuleucel-T on prostatic cancer tissue in the preoperative setting.MethodsPatients with untreated localized prostate cancer were treated on an open-label Phase II study of sipuleucel-T prior to planned radical prostatectomy (RP). Immune infiltrates in RP specimens (posttreatment) and in paired pretreatment biopsies were evaluated by immunohistochemistry (IHC). Correlations between circulating immune response and IHC were assessed using Spearman rank order.ResultsOf the 42 enrolled patients, 37 were evaluable. Adverse events were primarily transient, mild-to-moderate and infusion related. Patients developed T cell proliferation and interferon-Îł responses detectable in the blood following treatment. Furthermore, a greater-than-three-fold increase in infiltrating CD3(+), CD4(+) FOXP3(-), and CD8(+) T cells was observed in the RP tissues compared with the pretreatment biopsy (binomial proportions: all P < .001). This level of T cell infiltration was observed at the tumor interface, and was not seen in a control group consisting of 12 concurrent patients who did not receive any neoadjuvant treatment prior to RP. The majority of infiltrating T cells were PD-1(+) and Ki-67(+), consistent with activated T cells. Importantly, the magnitude of the circulating immune response did not directly correlate with T cell infiltration within the prostate based upon Spearman's rank order correlation.ConclusionsThis study is the first to demonstrate a local immune effect from the administration of sipuleucel-T. Neoadjuvant sipuleucel-T elicits both a systemic antigen-specific T cell response and the recruitment of activated effector T cells into the prostate tumor microenvironment
Photoionization Feedback in Low--Mass Galaxies at High Redshift
The cosmic ultraviolet (UV) ionizing background impacts the formation of
dwarf galaxies in the low-redshift universe (z=3) by suppressing gas infall
into galactic halos with circular velocities up to v(circ)=75 km/s. Using a
one-dimensional, spherically symmetric hydrodynamics code (Thoul & Weinberg
1995), we examine the effect of an ionizing background on low-mass galaxies
forming at high redshifts (z>10). We find that the importance of
photoionization feedback is greatly reduced, because (1) at high redshift,
dwarf-galaxy sized objects can self-shield against the ionizing background, (2)
collisional cooling processes at high redshift are more efficient, (3) the
amplitude of the ionizing background at high redshift is lower, and (4) the
ionizing radiation turns on when the perturbation that will become the dwarf
galaxy has already grown to a substantial overdensity. We find that because of
these reasons, gas can collect inside halos with circular velocities as low as
v(circ)=10 km/s. This result has important implications for the reionization
history of the universe.Comment: submitted to ApJ, 10 emulateapj pages with 4 figures include
Implications of Qudit Superselection rules for the Theory of Decoherence-free Subsystems
The use of d-state systems, or qudits, in quantum information processing is
discussed. Three-state and higher dimensional quantum systems are known to have
very different properties from two-state systems, i.e., qubits. In particular
there exist qudit states which are not equivalent under local unitary
transformations unless a selection rule is violated. This observation is shown
to be an important factor in the theory of decoherence-free, or noiseless,
subsystems. Experimentally observable consequences and methods for
distinguishing these states are also provided, including the explicit
construction of new decoherence-free or noiseless subsystems from qutrits.
Implications for simulating quantum systems with quantum systems are also
discussed.Comment: 13 pages, 1 figures, Version 2: Typos corrected, references fixed and
new ones added, also includes referees suggested changes and a new exampl
Where does Cosmological Perturbation Theory Break Down?
We apply the effective field theory approach to the coupled metric-inflaton
system, in order to investigate the impact of higher dimension operators on the
spectrum of scalar and tensor perturbations in the short-wavelength regime. In
both cases, effective corrections at tree-level become important when the
Hubble parameter is of the order of the Planck mass, or when the physical wave
number of a cosmological perturbation mode approaches the square of the Planck
mass divided by the Hubble constant. Thus, the cut-off length below which
conventional cosmological perturbation theory does not apply is likely to be
much smaller than the Planck length. This has implications for the
observability of "trans-Planckian" effects in the spectrum of primordial
perturbations.Comment: 25 pages, uses FeynM
Acromegaly, Mr Punch and caricature.
The origin of Mr Punch from the Italian Pulcinella of the Commedia dell'arte is well known but his feature, large hooked nose, protruding chin, kyphosis and sternal protrusion all in an exaggerated form also suggest the caricature of an acromegalic. This paper looks at the physical characteristics of acromegaly, the origin of Mr Punch and the development of caricature linking them together in the acromegalic caricature that now has a life of its own
The Effective Field Theory of Cosmological Large Scale Structures
Large scale structure surveys will likely become the next leading
cosmological probe. In our universe, matter perturbations are large on short
distances and small at long scales, i.e. strongly coupled in the UV and weakly
coupled in the IR. To make precise analytical predictions on large scales, we
develop an effective field theory formulated in terms of an IR effective fluid
characterized by several parameters, such as speed of sound and viscosity.
These parameters, determined by the UV physics described by the Boltzmann
equation, are measured from N-body simulations. We find that the speed of sound
of the effective fluid is c_s^2 10^(-6) and that the viscosity contributions
are of the same order. The fluid describes all the relevant physics at long
scales k and permits a manifestly convergent perturbative expansion in the size
of the matter perturbations \delta(k) for all the observables. As an example,
we calculate the correction to the power spectrum at order \delta(k)^4. The
predictions of the effective field theory are found to be in much better
agreement with observation than standard cosmological perturbation theory,
already reaching percent precision at this order up to a relatively short scale
k \sim 0.24 h/Mpc.Comment: v2: typos corrected, JHEP published versio
Spatial Degrees of Freedom in Everett Quantum Mechanics
Stapp claims that, when spatial degrees of freedom are taken into account,
Everett quantum mechanics is ambiguous due to a "core basis problem." To
examine an aspect of this claim I generalize the ideal measurement model to
include translational degrees of freedom for both the measured system and the
measuring apparatus. Analysis of this generalized model using the Everett
interpretation in the Heisenberg picture shows that it makes unambiguous
predictions for the possible results of measurements and their respective
probabilities. The presence of translational degrees of freedom for the
measuring apparatus affects the probabilities of measurement outcomes in the
same way that a mixed state for the measured system would. Examination of a
measurement scenario involving several observers illustrates the consistency of
the model with perceived spatial localization of the measuring apparatus.Comment: 34 pp., no figs. Introduction, discussion revised. Material
tangential to main point remove
Metastability in Two Dimensions and the Effective Potential
We study analytically and numerically the decay of a metastable phase in
(2+1)-dimensional classical scalar field theory coupled to a heat bath, which
is equivalent to two-dimensional Euclidean quantum field theory at zero
temperature. By a numerical simulation we obtain the nucleation barrier as a
function of the parameters of the potential, and compare it to the theoretical
prediction from the bounce (critical bubble) calculation. We find the
nucleation barrier to be accurately predicted by theory using the bounce
configuration obtained from the tree-level (``classical'') effective action.
Within the range of parameters probed, we found that using the bounce derived
from the one-loop effective action requires an unnaturally large prefactor to
match the lattice results. Deviations from the tree-level prediction are seen
in the regime where loop corrections would be expected to become important.Comment: 13pp, LaTex with Postscript figs, CLNS 93/1202, DART-HEP-93/0
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