323 research outputs found
Three-particle entanglement versus three-particle nonlocality
The notions of three-particle entanglement and three-particle nonlocality are
discussed in the light of Svetlichny's inequality [Phys. Rev. D 35, 3066
(1987)]. It is shown that there exist sets of measurements which can be used to
prove three-particle entanglement, but which are nevertheless useless at
proving three-particle nonlocality. In particular, it is shown that the quantum
predictions giving a maximal violation of Mermin's three-particle Bell
inequality [Phys. Rev. Lett. 65, 1838 (1990)] can be reproduced by a hybrid
hidden variables model in which nonlocal correlations are present only between
two of the particles. It should be possible, however, to test the existence of
both three-particle entanglement and three-particle nonlocality for any given
quantum state via Svetlichny's inequality.Comment: REVTeX4, 4 pages, journal versio
Better detection of Multipartite Bound Entanglement with Three-Setting Bell Inequalities
It was shown in Phys. Rev. Lett., 87, 230402 (2001) that N (N >= 4) qubits
described by a certain one parameter family F of bound entangled states violate
Mermin-Klyshko inequality for N >= 8. In this paper we prove that the states
from the family F violate Bell inequalities derived in Phys. Rev. A, 56, R1682
(1997), in which each observer measures three non-commuting sets of orthogonal
projectors, for N >=7. We also derive a simple one parameter family of
entanglement witnesses that detect entanglement for all the states belonging to
F. It is possible that these new entanglement witnesses could be generated by
some Bell inequalities.Comment: Revtex4, 1 figur
Massless Minimally Coupled Fields in De Sitter Space: O(4)-Symmetric States Versus De Sitter Invariant Vacuum
The issue of de Sitter invariance for a massless minimally coupled scalar
field is revisited. Formally, it is possible to construct a de Sitter invariant
state for this case provided that the zero mode of the field is quantized
properly. Here we take the point of view that this state is physically
acceptable, in the sense that physical observables can be computed and have a
reasonable interpretation. In particular, we use this vacuum to derive a new
result: that the squared difference between the field at two points along a
geodesic observer's space-time path grows linearly with the observer's proper
time for a quantum state that does not break de Sitter invariance. Also, we use
the Hadamard formalism to compute the renormalized expectation value of the
energy momentum tensor, both in the O(4) invariant states introduced by Allen
and Follaci, and in the de Sitter invariant vacuum. We find that the vacuum
energy density in the O(4) invariant case is larger than in the de Sitter
invariant case.Comment: TUTP-92-1, to appear in Phys. Rev.
Decoupling in an expanding universe: boundary RG-flow affects initial conditions for inflation
We study decoupling in FRW spacetimes, emphasizing a Lagrangian description
throughout. To account for the vacuum choice ambiguity in cosmological
settings, we introduce an arbitrary boundary action representing the initial
conditions. RG flow in these spacetimes naturally affects the boundary
interactions. As a consequence the boundary conditions are sensitive to
high-energy physics through irrelevant terms in the boundary action. Using
scalar field theory as an example, we derive the leading dimension four
irrelevant boundary operators. We discuss how the known vacuum choices, e.g.
the Bunch-Davies vacuum, appear in the Lagrangian description and square with
decoupling. For all choices of boundary conditions encoded by relevant boundary
operators, of which the known ones are a subset, backreaction is under control.
All, moreover, will generically feel the influence of high-energy physics
through irrelevant (dimension four) boundary corrections. Having established a
coherent effective field theory framework including the vacuum choice
ambiguity, we derive an explicit expression for the power spectrum of
inflationary density perturbations including the leading high energy
corrections. In accordance with the dimensionality of the leading irrelevant
operators, the effect of high energy physics is linearly proportional to the
Hubble radius H and the scale of new physics L= 1/M.Comment: LaTeX plus axodraw figures. v2: minor corrections; refs added. JHEP
style: 34 pages + 18 pages appendi
Production and detection of three-qubit entanglement in the Fermi sea
Building on a previous proposal for the entanglement of electron-hole pairs
in the Fermi sea, we show how 3 qubits can be entangled without using
electron-electron interactions. As in the 2-qubit case, this electronic scheme
works even if the sources are in (local) thermal equilibrium -- in contrast to
the photonic analogue. The 3 qubits are represented by 4 edge-channel
excitations in the quantum Hall effect (2 hole excitations plus 2 electron
excitations with identical channel index). The entangler consists of an
adiabatic point contact flanked by a pair of tunneling point contacts. The
irreducible 3-qubit entanglement is characterized by the tangle, which is
expressed in terms of the transmission matrices of the tunneling point
contacts. The maximally entangled Greenberger-Horne-Zeilinger (GHZ) state is
obtained for channel-independent tunnel probabilities. We show how
low-frequency noise measurements can be used to determine an upper and lower
bound to the tangle. The bounds become tighter the closer the electron-hole
state is to the GHZ state.Comment: 8 pages including 4 figures; [2017: fixed broken postscript figures
Super-Hubble de Sitter Fluctuations and the Dynamical RG
Perturbative corrections to correlation functions for interacting theories in
de Sitter spacetime often grow secularly with time, due to the properties of
fluctuations on super-Hubble scales. This growth can lead to a breakdown of
perturbation theory at late times. We argue that Dynamical Renormalization
Group (DRG) techniques provide a convenient framework for interpreting and
resumming these secularly growing terms. In the case of a massless scalar field
in de Sitter with quartic self-interaction, the resummed result is also less
singular in the infrared, in precisely the manner expected if a dynamical mass
is generated. We compare this improved infrared behavior with large-N
expansions when applicable.Comment: 33 pages, 4 figure
Renormalization Group and Decoupling in Curved Space: II. The Standard Model and Beyond
We continue the study of the renormalization group and decoupling of massive
fields in curved space, started in the previous article and analyse the higher
derivative sector of the vacuum metric-dependent action of the Standard Model.
The QCD sector at low-energies is described in terms of the composite effective
fields. For fermions and scalars the massless limit shows perfect
correspondence with the conformal anomaly, but similar limit in a massive
vector case requires an extra compensating scalar. In all three cases the
decoupling goes smoothly and monotonic. A particularly interesting case is the
renormalization group flow in the theory with broken supersymmetry, where the
sign of one of the beta-functions changes on the way from the UV to IR.Comment: 27 pages, 8 figure
Clinical Outcomes and Survival Following Treatment of Metastatic Castrate-Refractory Prostate Cancer With Docetaxel Alone or With Strontium-89, Zoledronic Acid, or Both
Importance Bony metastatic castrate-refractory prostate cancer (CRPC) has a poor prognosis and high morbidity. Zoledronic acid (ZA) is commonly combined with docetaxel in practice but lacks evidence that combining is effective, and strontium-89 (Sr89) is generally used palliatively in patients unfit for chemotherapy. Phase 2 analysis of the TRAPEZE trial confirmed combining the agents was safe and feasible, and the objectives of phase 3 include assessment of the treatments on survival.
Objective To determine clinical effectiveness and cost-effectiveness of combining docetaxel, ZA, and Sr89, all having palliative benefits and used in bony metastatic CRPC to control bone symptoms and, for docetaxel, to prolong survival.
Design, Setting, and Participants The TRAPEZE trial is a 2 × 2 factorial trial comparing docetaxel alone or with ZA, Sr89, or both. A cohort of 757 participants were recruited between February 2005 and February 2012 from hospitals in the United Kingdom. Overall, 169 participants (45%) had received palliative radiotherapy, and the median (IQR) prostate-specific antigen level was 146 (51-354). Follow-ups were performed for at least 12 months.
Interventions Up to 10 cycles of docetaxel alone; docetaxel with ZA; docetaxel with a single Sr89 dose after 6 cycles; or docetaxel with both ZA and Sr89.
Main Outcomes and Measures Primary outcomes included clinical progression-free survival (CPFS) (pain progression, skeletal-related events [SREs], or death) and cost-effectiveness. Secondary outcomes included SRE-free interval, pain progression–free interval, total SREs, and overall survival (OS).
Results Overall, of 757 participants, 349 (46%) completed docetaxel treatment. Median (IQR) age was 68 (63-73) years. Clinical progression-free survival did not reach statistical significance for either Sr89 or ZA. Cox regression analysis adjusted for all stratification variables showed benefit of Sr89 on CPFS (hazard ratio [HR], 0.85; 95% CI, 0.73-0.99; P = .03) and confirmed no effect of ZA (HR, 0.98; 95% CI, 0.85-1.14; P = .81); ZA had a significant effect on SRE-free interval (HR, 0.78; 95% CI, 0.65-0.95; P = .01). For OS, there was no effect of either Sr89 (HR, 0.92; 95% CI, 0.79-1.08; P = 0.34) or ZA (HR, 0.99; 95% CI, 0.84-1.16; P = 0.91).
Conclusions and Relevance Strontium-89 combined with docetaxel improved CPFS but did not improve OS, SRE-free interval, or total SREs; ZA did not improve CPFS or OS but did significantly improve median SRE-free interval and reduced total SREs by around one-third, suggesting a role as postchemotherapy maintenance therapy
Non-vacuum Solutions of Bianchi Type VI_0 Universe in f(R) Gravity
In this paper, we solve the field equations in metric f(R) gravity for
Bianchi type VI_0 spacetime and discuss evolution of the expanding universe. We
find two types of non-vacuum solutions by taking isotropic and anisotropic
fluids as the source of matter and dark energy. The physical behavior of these
solutions is analyzed and compared in the future evolution with the help of
some physical and geometrical parameters. It is concluded that in the presence
of isotropic fluid, the model has singularity at and represents
continuously expanding shearing universe currently entering into phantom phase.
In anisotropic fluid, the model has no initial singularity and exhibits the
uniform accelerating expansion. However, the spacetime does not achieve
isotropy as in both of these solutions.Comment: 20 pages, 5 figures, accepted for publication in Astrophys. Space Sc
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
- …