29 research outputs found
Quantum gravity at a TeV and the renormalization of Newton's constant
We examine whether renormalization effects can cause NewtonÂżs constant to change dramatically with energy, perhaps even reducing the scale of quantum gravity to the TeV region without the introduction of extra dimensions. We examine a model that realizes this possibility and describe experimental signatures from the production of small black holes
Trace Anomaly of Dilaton Coupled Scalars in Two Dimensions
Conformal scalar fields coupled to the dilaton appear naturally in
two-dimensional models of black hole evaporation. We calculate their trace
anomaly. It follows that an RST-type counterterm appears naturally in the
one-loop effective action.Comment: 11 pages, LaTeX2e; submitted to Phys. Rev. Lett., minor change
One-loop theory in Robertson-Walker spacetimes: adiabatic regularization and analytic approximation
The renormalization of a scalar field theory with a quartic self-coupling (a
theory) via adiabatic regularization in a general
Robertson-Walker spacetime is discussed. The adiabatic counterterms are
presented in a way that is most conducive to numerical computations. A
variation of the adiabatic regularization method is presented which leads to
analytic approximations for the energy-momentum tensor of the field and the
quantum contribution to the effective mass of the mean field. Conservation of
the energy-momentum tensor for the field is discussed and it is shown that the
part of the energy-momentum tensor which depends only on the mean field is not
conserved but the full renormalized energy-momentum tensor is conserved as
expected and required by the semiclassical Einstein's equation. It is also
shown that if the analytic approximations are used then the resulting
approximate energy-momentum tensor is conserved. This allows a self-consistent
backreaction calculation to be performed using the analytic approximations. The
usefulness of the approximations is discussed.Comment: 12 pages in revtex, and no figure
Non-Extreme and Ultra-Extreme Domain Walls and Their Global Space-Times
Non-extreme walls (bubbles with two insides) and ultra-extreme walls (bubbles
of false vacuum decay) are discussed. Their respective energy densities are
higher and lower than that of the corresponding extreme (supersymmetric),
planar domain wall. These singularity free space-times exhibit non-trivial
causal structure analogous to certain non-extreme black holes. We focus on
anti-de~Sitter--Minkowski walls and comment on Minkowski--Minkowski walls with
trivial extreme limit, as well as walls adjacent to de~Sitter space-times with
no extreme limit.Comment: Revised version, 4 pages of REVTEX, UPR-546-T/Rev. Two figures not
included. This version contains further elaboration of the space-time causal
structur
Cauchy Horizons, Thermodynamics and Closed Time-like Curves in Planar Supersymmetric Space-times
We study geodesically complete, singularity free space-times induced by
supersymmetric planar domain walls interpolating between Minkowski and anti-de
Sitter () vacua. A geodesically complete space-time without closed
time-like curves includes an infinite number of semi-infinite Minkowski
space-times, separated from each other by a region of space-time. These
space-times are closely related to the extreme Reissner Nordstr\" om (RN) black
hole, exhibiting Cauchy horizons with zero Hawking temperature, but in contrast
to the RN black hole there is no entropy. Another geodesically complete
extension with closed time-like curves involves space-times connecting a finite
number of semi-infinite Minkowski space-times.Comment: 11 pages, 1 figure appended, phyzz
Wave Propagation in Stochastic Spacetimes: Localization, Amplification and Particle Creation
Here we study novel effects associated with electromagnetic wave propagation
in a Robertson-Walker universe and the Schwarzschild spacetime with a small
amount of metric stochasticity. We find that localization of electromagnetic
waves occurs in a Robertson-Walker universe with time-independent metric
stochasticity, while time-dependent metric stochasticity induces exponential
instability in the particle production rate. For the Schwarzschild metric,
time-independent randomness can decrease the total luminosity of Hawking
radiation due to multiple scattering of waves outside the black hole and gives
rise to event horizon fluctuations and thus fluctuations in the Hawking
temperature.Comment: 26 pages, 1 Postscript figure, submitted to Phys. Rev. D on July 29,
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The Magnitude of Androgen Receptor Positivity in Breast Cancer Is Critical for Reliable Prediction of Disease Outcome
Purpose: Consensus is lacking regarding the androgen receptor (AR) as a prognostic marker in breast cancer. The objectives of this study were to comprehensively review the literature on AR prognostication and determine optimal criteria for AR as an independent predictor of breast cancer survival. Experimental Design: AR positivity was assessed by immunostaining in two clinically validated primary breast cancer cohorts [training cohort, n = 219; validation cohort, n = 418; 77% and 79% estrogen receptor alpha (ERα) positive, respectively]. The optimal AR cut-point was determined by ROC analysis in the training cohort and applied to both cohorts. Results: AR was an independent prognostic marker of breast cancer outcome in 22 of 46 (48%) previous studies that performed multivariate analyses. Most studies used cut-points of 1% or 10% nuclear positivity. Herein, neither 1% nor 10% cut-points were robustly prognostic. ROC analysis revealed that a higher AR cut-point (78% positivity) provided optimal sensitivity and specificity to predict breast cancer survival in the training (HR, 0.41; P = 0.015) and validation (HR, 0.50; P = 0.014) cohorts. Tenfold cross-validation confirmed the robustness of this AR cut-point. Patients with ERα-positive tumors and AR positivity â„78% had the best survival in both cohorts (P 0.87) had the best outcomes (P < 0.0001). Conclusions: This study defines an optimal AR cut-point to reliably predict breast cancer survival. Testing this cut-point in prospective cohorts is warranted for implementation of AR as a prognostic factor in the clinical management of breast cancer
Progesterone receptor modulates ERα action in breast cancer.
Progesterone receptor (PR) expression is used as a biomarker of oestrogen receptor-α (ERα) function and breast cancer prognosis. Here we show that PR is not merely an ERα-induced gene target, but is also an ERα-associated protein that modulates its behaviour. In the presence of agonist ligands, PR associates with ERα to direct ERα chromatin binding events within breast cancer cells, resulting in a unique gene expression programme that is associated with good clinical outcome. Progesterone inhibited oestrogen-mediated growth of ERα(+) cell line xenografts and primary ERα(+) breast tumour explants, and had increased anti-proliferative effects when coupled with an ERα antagonist. Copy number loss of PGR, the gene coding for PR, is a common feature in ERα(+) breast cancers, explaining lower PR levels in a subset of cases. Our findings indicate that PR functions as a molecular rheostat to control ERα chromatin binding and transcriptional activity, which has important implications for prognosis and therapeutic interventions.We would like to acknowledge the support of the University of Cambridge, Cancer Research UK and Hutchison Whampoa Limited. Research reported in this manuscript was supported by the National Cancer Institute of the National Institutes of Health under award number 5P30CA142543 (to UT Southwestern) and Department of Defense grants W81XWH-12-1-0288-03 (GVR). W.D.T. is supported by grants from the National Health and Medical Research Council of Australia (ID 1008349; ID 1084416) and Cancer Australia (ID 627229) T.E.H held a Fellowship Award from the US Department of Defense Breast Cancer Research Program (BCRP; #W81XWH-11-1-0592) and currently is supported by a Florey Fellowship from the Royal Adelaide Hospital Research Foundation. J.S.C is supported by an ERC starting grant and an EMBO Young investigator award.This is the accepted manuscript. The final version is available at www.nature.com/nature/journal/v523/n7560/full/nature14583.htm
Local and global gravitational aspects of domain wall space-times
Local and global gravitational effects induced by eternal vacuum domain walls
are studied. We concentrate on thin walls between non-equal and non-positive
cosmological constants on each side of the wall. These vacuum domain walls fall
in three classes depending on the value of their energy density : (1)\
extreme walls with are planar, static walls
corresponding to supersymmetric configurations, (2)\ non-extreme walls with
correspond to
expanding bubbles with observers on either side of the wall being {\em
inside\/} the bubble, and (3)\ ultra-extreme walls with represent the bubbles of false
vacuum decay. On the sides with less negative cosmological constant, the
extreme, non-extreme, and ultra-extreme walls exhibit no, repulsive, and
attractive effective ``gravitational forces,'' respectively. These
``gravitational forces'' are global effects not caused by local curvature.
Since the non-extreme wall encloses observers on both sides, the supersymmetric
system has the lowest gravitational mass accessable to outside observers. It is
conjectured that similar positive mass protection occurs in all physical
systems and that no finite negative mass object can exist inside the universe.
We also discuss the global space-time structure of these singularity free
space-times and point out intriguing analogies with the causal structure of
black holes.Comment: UPR-565-T, 26 REVTEX pages, 10 figures available upon reques
Initial Conditions for Inflation
Free scalar fields in de Sitter space have a one-parameter family of states
invariant under the de Sitter group, including the standard thermal vacuum. We
show that, except for the thermal vacuum, these states are unphysical when
gravitational interactions are included. We apply these observations to the
quantum state of the inflaton, and find that, at best, dramatic fine tuning is
required for states other than the thermal vacuum to lead to observable
features in the CMBR anisotropy.Comment: 31 pages, 4 figure