Trouton-Noble paradox revisited

An apparent paradox is obtained in all previous treatments of the Trouton-Noble experiment; there is a three-dimensional torque in an inertial frame S in which a thin parallel-plate capacitor is moving, but there is no 3D torque in S', the rest frame of the capacitor. In this paper instead of using 3D quantities and their ``apparent'' transformations we deal with 4D geometric quantities their Lorentz transformations and equations with them. We introduce a new decomposition of the torque N (bivector) into 1-vectors N_{s} and N_{t}. It is shown that in the frame of ``fiducial'' observers, in which the observers who measure N_{s} and N_{t} are at rest, and in the standard basis, only the spatial components N_{s}^{i} and N_{t}^{i} remain, which can be associated with components of two 3D torques. In such treatment with 4D geometric quantities the mentioned paradox does not appear. The presented explanation is in a complete agreement with the principle of relativity and with the Trouton-Noble experiment without the introduction of any additional torque

Membrane paradigm realized?

Are there any degrees of freedom on the black hole horizon? Using the `membrane paradigm' we can reproduce coarse-grained physics outside the hole by assuming a fictitious membrane just outside the horizon. But to solve the information puzzle we need `real' degrees of freedom at the horizon, which can modify Hawking's evolution of quantum modes. We argue that recent results on gravitational microstates imply a set of real degrees of freedom just outside the horizon; the state of the hole is a linear combination of rapidly oscillating gravitational solutions with support concentrated just outside the horizon radius. The collective behavior of these microstate solutions may give a realization of the membrane paradigm, with the fictitious membrane now replaced by real, explicit degrees of freedom.Comment: 8 pages, Latex, 3 figures (Essay given second place in Gravity Research Foundation essay competition 2010

Glassy nature of stripe ordering in La(1.6-x)Nd(0.4)Sr(x)CuO(4)

We present the results of neutron-scattering studies on various aspects of crystalline and magnetic structure in single crystals of La(1.6-x)Nd(0.4)Sr(x)CuO(4) with x=0.12 and 0.15. In particular, we have reexamined the degree of stripe order in an x=0.12 sample. Measurements of the width for an elastic magnetic peak show that it saturates at a finite value below 30 K, corresponding to a spin-spin correlation length of 200 A. A model calculation indicates that the differing widths of magnetic and (previously reported) charge-order peaks, together with the lack of commensurability, can be consistently explained by disorder in the stripe spacing. Above 30 K, the width of the nominally elastic signal begins to increase. Interpreting the signal as critical scattering from slowly fluctuating spins, the temperature dependence of the width is consistent with renormalized classical behavior of a 2-dimensional anisotropic Heisenberg antiferromagnet. Inelastic scattering measurements show that incommensurate spin excitations survive at and above 50 K, where the elastic signal is neglible. We also report several results related to the LTO-to-LTT transition.Comment: 13 pp, 2-col. REVTeX, 11 figures embedded with psfig; expanded discussion of T-dep. of magnetic peak width; version to appear in Phys. Rev. B (01Jun99

Exponential Decay of Correlations Implies Area Law

We prove that a finite correlation length, i.e. exponential decay of correlations, implies an area law for the entanglement entropy of quantum states defined on a line. The entropy bound is exponential in the correlation length of the state, thus reproducing as a particular case Hastings proof of an area law for groundstates of 1D gapped Hamiltonians. As a consequence, we show that 1D quantum states with exponential decay of correlations have an efficient classical approximate description as a matrix product state of polynomial bond dimension, thus giving an equivalence between injective matrix product states and states with a finite correlation length. The result can be seen as a rigorous justification, in one dimension, of the intuition that states with exponential decay of correlations, usually associated with non-critical phases of matter, are simple to describe. It also has implications for quantum computing: It shows that unless a pure state quantum computation involves states with long-range correlations, decaying at most algebraically with the distance, it can be efficiently simulated classically. The proof relies on several previous tools from quantum information theory - including entanglement distillation protocols achieving the hashing bound, properties of single-shot smooth entropies, and the quantum substate theorem - and also on some newly developed ones. In particular we derive a new bound on correlations established by local random measurements, and we give a generalization to the max-entropy of a result of Hastings concerning the saturation of mutual information in multiparticle systems. The proof can also be interpreted as providing a limitation on the phenomenon of data hiding in quantum states.Comment: 35 pages, 6 figures; v2 minor corrections; v3 published versio

Spin Excitations in La2CuO4: Consistent Description by Inclusion of Ring-Exchange

We consider the square lattice Heisenberg antiferromagnet with plaquette ring exchange and a finite interlayer coupling leading to a consistent description of the spin-wave excitation spectrum in La2CuO4. The values of the in-plane exchange parameters, including ring-exchange J_{\Box}, are obtained consistently by an accurate fit to the experimentally observed in-plane spin-wave dispersion, while the out-of-plane exchange interaction is found from the temperature dependence of the sublattice magnetization at low temperatures. The fitted exchange interactions J=151.9 meV and J_{\Box}=0.24 J give values for the spin stiffness and the Neel temperature in excellent agreement with the experimental data.Comment: 4 pages, 1 figure, RevTe

Quantum Oscillation Studies of the Fermi Surface of LaFePO

We review recent experimental measurements of the Fermi surface of the iron-pnictide superconductor LaFePO using quantum oscillation techniques. These studies show that the Fermi surface topology is close to that predicted by first principles density functional theory calculations, consisting of quasi-two-dimensional electron-like and hole-like sheets. The total volume of the two hole sheets is almost equal to that of the two electron sheets, and the hole and electron Fermi surface sheets are close to a nesting condition. No evidence for the predicted three dimensional pocket arising from the Fe $d_{z^2}$ band is found. Measurements of the effective mass suggest a renormalisation of around two, close to the value for the overall band renormalisation found in recent angle resolved photoemission measurements.Comment: Submitted to Physica C special issue on iron-pnictide superconductor

Adherence to a MIND-Like Dietary Pattern, Long-Term Exposure to Fine Particulate Matter Air Pollution, and MRI-Based Measures of Brain Volume: The Women’s Health Initiative Memory Study-MRI

BACKGROUND: Previous studies suggest that certain dietary patterns and constituents may be beneficial to brain health. Airborne exposures to fine particulate matter [particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5)] are neurotoxic, but the combined effects of dietary patterns and PM2.5 have not been investigated. OBJECTIVES: We examined whether previously reported association between PM2.5 exposure and lower white matter volume (WMV) differed between women whose usual diet during the last 3 months before baseline was more or less consistent with a Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND)-like diet, a dietary pattern that may slow neurodegenerative changes. METHODS: This study included 1,302 U.S. women who were 65-79 y old and free of dementia in the period 1996-1998 (baseline). In the period 2005-2006, structural brain magnetic resonance imaging (MRI) scans were performed to estimate normal-appearing brain volumes (excluding areas with evidence of small vessel ischemic disease). Baseline MIND diet scores were derived from a food frequency questionnaire. Three-year average PM2.5 exposure prior to MRI was estimated using geocoded participant addresses and a spatiotemporal model. RESULTS: Average total and temporal lobe WMVs were 0:74 cm3 [95% confidence interval (CI): 0.001, 1.48) and 0:19 cm3 (95% CI: 0.002, 0.37) higher, respectively, with each 0.5-point increase in the MIND score and were 4:16 cm3 (95% CI: -6:99, -1:33) and 1:46 cm3 (95% CI: -2:16, -0:76) lower, respectively, with each interquartile range (IQR) (IQR = 3:22 μg/m3) increase in PM2.5. The inverse association between PM2.5 per IQR and WMV was stronger (p-interaction <0:001) among women with MIND scores below the median (for total WMV, -12:47 cm3; 95% CI: −17:17, −7:78), but absent in women with scores above the median (0:16 cm3; 95% CI: −3:41, 3.72), with similar patterns for WMV in the frontal, parietal, and temporal lobes. For total cerebral and hippocampus brain volumes or WMV in the corpus callosum, the associations with PM2.5 were not significantly different for women with high MIND scores and women with low MIND scores

Pharmacogenomics of Vincristine-Induced Peripheral Neuropathy Implicates Pharmacokinetic and Inherited Neuropathy Genes

Vincristine is an effective chemotherapeutic drug for various cancers, including acute lymphoblastic leukemia (ALL). Unfortunately, clinical utility is restricted by dose-limiting vincristine-induced peripheral neuropathies (VIPN). We sought to determine the association of VIPN with a recently identified risk variant, CEP72 rs924607, and drug absorption, distribution, metabolism, and excretion (ADME) gene variants in pediatric ALL. This was followed by a meta-analysis of pharmacogenomic data from over 500 patients. CEP72 rs924607 was significantly associated with VIPN (P = 0.02; odds ratio (OR) = 3.4). ADME analyses identified associations between VIPN and ABCC1 rs3784867 (P = 5.34 × 10 −5 ; OR = 4.9), and SLC5A7 rs1013940 (P = 9.00 × 10 −4 ; OR= 8.6); genes involved in vincristine transport and inherited neuropathies, respectively. Meta-analysis identified an association with a variant related to TTPA (rs10504361: P = 6.85 × 10 −4 ; OR = 2.0), a heritable neuropathy-related gene. This study provides essential corroboratory evidence for CEP72 rs924607 and highlights the importance of drug transporter and inherited neuropathy genes in VIPN

B vitamin intakes modify the association between particulate air pollutants and incidence of all-cause dementia: Findings from the Women's Health Initiative Memory Study

Introduction: Particulate air pollutants may induce neurotoxicity by increasing homocysteine levels, which can be lowered by high B vitamin intakes. Therefore, we examined whether intakes of three B vitamins (folate, B12, and B6) modified the association between PM2.5 exposure and incidence of all-cause dementia. Methods: This study included 7183 women aged 65 to 80 years at baseline. B vitamin intakes from diet and supplements were estimated by food frequency questionnaires at baseline. The 3-year average PM2.5 exposure was estimated using a spatiotemporal model. Results: During a mean follow-up of 9 years, 342 participants developed all-cause dementia. We found that residing in locations with PM2.5 exposure above the regulatory standard (12 μg/m3) was associated with a higher risk of dementia only among participants with lower intakes of these B vitamins. Discussion: This is the first study suggesting that the putative neurotoxicity of PM2.5 exposure may be attenuated by high B vitamin intakes