30 research outputs found
Testing axioms for Quantum Mechanics on Probabilistic toy-theories
In Ref. [1] one of the authors proposed postulates for axiomatizing Quantum
Mechanics as a "fair operational framework", namely regarding the theory as a
set of rules that allow the experimenter to predict future events on the basis
of suitable tests, having local control and low experimental complexity. In
addition to causality, the following postulates have been considered: PFAITH
(existence of a pure preparationally faithful state), and FAITHE (existence of
a faithful effect). These postulates have exhibited an unexpected theoretical
power, excluding all known nonquantum probabilistic theories. Later in Ref. [2]
in addition to causality and PFAITH, postulate LDISCR (local discriminability)
and PURIFY (purifiability of all states) have been considered, narrowing the
probabilistic theory to something very close to Quantum Mechanics. In the
present paper we test the above postulates on some nonquantum probabilistic
models. The first model, "the two-box world" is an extension of the
Popescu-Rohrlich model, which achieves the greatest violation of the CHSH
inequality compatible with the no-signaling principle. The second model "the
two-clock world" is actually a full class of models, all having a disk as
convex set of states for the local system. One of them corresponds to the "the
two-rebit world", namely qubits with real Hilbert space. The third model--"the
spin-factor"--is a sort of n-dimensional generalization of the clock. Finally
the last model is "the classical probabilistic theory". We see how each model
violates some of the proposed postulates, when and how teleportation can be
achieved, and we analyze other interesting connections between these postulate
violations, along with deep relations between the local and the non-local
structures of the probabilistic theory.Comment: Submitted to QIP Special Issue on Foundations of Quantum Informatio
Symmetric Points in the Landscape as Cosmological Attractors
In the landscape, if there is to be any prospect of scientific prediction, it
is crucial that there be states which are distinguished in some way. The
obvious candidates are states which exhibit symmetries. Here we focus on states
which exhibit discrete symmetries. Such states are rare, but one can speculate
that they are cosmological attractors. We investigate the problem in model
landscapes and cosmologies which capture some of the features of candidate flux
landscapes. In non-supersymmetric theories we find no evidence that such states
might be cosmologically favored. In supersymmetric theories, simple arguments
suggest that states which exhibit symmetries might be. Our considerations
lead us to raise questions about some popular models of eternal inflation.Comment: 27 pages, latex, minor typo correcte
Greenberger-Horne-Zeilinger nonlocality for continuous variable systems
As a development of our previous work, this paper is concerned with the
Greenberger-Horne-Zeilinger (GHZ) nonlocality for continuous variable cases.
The discussion is based on the introduction of a pseudospin operator, which has
the same algebra as the Pauli operator, for each of the modes of a light
field. Then the Bell-CHSH (Clauser, Horne, Shimony and Holt) inequality is
presented for the modes, each of which has a continuous degree of freedom.
Following Mermin's argument, it is demonstrated that for -mode
parity-entangled GHZ states (in an infinite-dimensional Hilbert space) of the
light field, the contradictions between quantum mechanics and local realism
grow exponentially with , similarly to the usual -spin cases.Comment: RevTEX; comments are welcomed; new version with minor change
Deforming, revolving and resolving - New paths in the string theory landscape
In this paper we investigate the properties of series of vacua in the string
theory landscape. In particular, we study minima to the flux potential in type
IIB compactifications on the mirror quintic. Using geometric transitions, we
embed its one dimensional complex structure moduli space in that of another
Calabi-Yau with h^{1,1}=86 and h^{2,1}=2. We then show how to construct
infinite series of continuously connected minima to the mirror quintic
potential by moving into this larger moduli space, applying its monodromies,
and moving back. We provide an example of such series, and discuss their
implications for the string theory landscape.Comment: 41 pages, 5 figures; minor corrections, published versio
Hamiltonian dynamics and Noether symmetries in Extended Gravity Cosmology
We discuss the Hamiltonian dynamics for cosmologies coming from Extended
Theories of Gravity. In particular, minisuperspace models are taken into
account searching for Noether symmetries. The existence of conserved quantities
gives selection rule to recover classical behaviors in cosmic evolution
according to the so called Hartle criterion, that allows to select correlated
regions in the configuration space of dynamical variables. We show that such a
statement works for general classes of Extended Theories of Gravity and is
conformally preserved. Furthermore, the presence of Noether symmetries allows a
straightforward classification of singularities that represent the points where
the symmetry is broken. Examples of nonminimally coupled and higher-order
models are discussed.Comment: 20 pages, Review paper to appear in EPJ
Bianchi solutions of quadratic gravity
It is believed that soon after the Planck time, Einstein's general relativity
theory should be corrected to an effective quadratic theory. Numerical
solutions for the anisotropic generalization of the Friedmann "open" model for this effective gravity are given. It must be emphasized that although
numeric, these solutions are exact in the sense that they depend only on the
precision of the machine. The solutions are identified asymptotically in a
certain way. It is found solutions which asymptote de Sitter space, Riemann
flat space and a singularity. The question of isotropisation of an initially
anisotropic Universe is of great importance in the context of cosmology.
Although isotropisation is not directly discussed in this present work, we show
that sufficiently small anisotropies, do not increase indefinitely according to
particular quadratic gravity theories. It can be understood as weak
isotropisation, and we stress that this result is strongly dependent on initial
conditions.Comment: version accepted for publication in General Relativity and
Gravitation. arXiv admin note: substantial text overlap with arXiv:1203.688
The Born Rule Dies
The Born rule may be stated mathematically as the rule that probabilities in
quantum theory are expectation values of a complete orthogonal set of
projection operators. This rule works for single laboratory settings in which
the observer can distinguish all the different possible outcomes corresponding
to the projection operators. However, theories of inflation suggest that the
universe may be so large that any laboratory, no matter how precisely it is
defined by its internal state, may exist in a large number of very distantly
separated copies throughout the vast universe. In this case, no observer within
the universe can distinguish all possible outcomes for all copies of the
laboratory. Then normalized probabilities for the local outcomes that can be
locally distinguished cannot be given by the expectation values of any
projection operators. Thus the Born rule dies and must be replaced by another
rule for observational probabilities in cosmology. The freedom of what this new
rule is to be is the measure problem in cosmology. A particular volume-averaged
form is proposed.Comment: LaTeX, 16 pages, typos in Eqs. (4.3) and (6.2) correcte
Lipid Emulsion Combined with Epinephrine and Vasopressin Does Not Improve Survival in a Swine Model of Bupivacaine-induced Cardiac Arrest
Background: This study sought to evaluate the efficacy of lipid emulsion in reversing bupivacaine-induced cardiovascular collapse when added to a resuscitation protocol that included the use of epinephrine and vasopressin. Methods: After induction of general anesthesia and instrumentation, 19 mixed-breed domestic swine had cardiovascular collapse induced by an intravenous bolus of 10 mg/kg bupivacaine. After 5 min of resuscitation including chest compressions, epinephrine (100 g/kg) and vasopressin (1.5 U/kg), animals were randomized to receive either a bolus of 20% lipid emulsion (4 ml/kg) followed by a continuous infusion (0.5 ml · kg ؊1 · mi
Maternal allergic asthma during pregnancy alters fetal lung and immune development in sheep: potential mechanisms for programming asthma and allergy
KEY POINTS:Experimental maternal allergic asthma in sheep provides an experimental model in which to test impacts on progeny. Fetuses from allergic asthmatic ewes had fewer surfactant-producing cells in lungs. A greater proportion of lymphocytes from thymus were CD44 positive in fetuses from allergic asthmatic ewes than in controls. These changes to fetal development might contribute to poor neonatal lung function and increased risk of allergy seen in offspring of pregnancies complicated by asthma. ABSTRACT:Asthma is prevalent in pregnancy and increases the risk of disease in offspring, including neonatal respiratory distress and childhood asthma and allergy, but the mechanisms are not understood. We hypothesized that fetal lung structure and immune phenotype in late gestation fetal sheep would be impaired in our sheep model of maternal allergic asthma during pregnancy. Singleton-bearing ewes were either sensitized before pregnancy to house dust mite (HDM, allergic, n = 7) or were non-allergic (control, n = 5). The ewes were subsequently subjected to repeated airway challenges with HDM (allergic group) or saline (control group) throughout gestation. Tissues were collected at 140 ± 1 days gestational age (term, ∼147 days). The density of type II alveolar epithelial cells (surfactant protein C-immunostained) in the lungs was 30% lower in fetuses from allergic ewes than in controls (P < 0.001), but tissue-to-air space ratio and numbers of leucocytes and macrophages were not different between groups. The proportion of CD44+ lymphocytes in the fetal thymus was 3.5-fold higher in fetuses from allergic ewes than in control ewes (P = 0.043). Fewer surfactant-producing type II alveolar epithelial cells may contribute to the increased risk of neonatal respiratory distress in infants of asthmatic mothers, suggesting that interventions to promote lung maturation could improve their neonatal outcomes. If the elevated lymphocyte expression of CD44 persists postnatally, this would confer greater susceptibility to allergic diseases in progeny of asthmatic mothers, consistent with observations in humans. Further experiments are needed to evaluate postnatal phenotypes of progeny and investigate potential interventions.Amy L. Wooldridge, Vicki L. Clifton, Timothy J. M. Moss, Hui Lu, Monerih Jamali, Stefanie Agostino, Beverly S. Muhlhausler, Janna L. Morrison, Robert De Matteo, Megan J. Wallace, Robert J. Bischof, Kathryn L. Gatfor