다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

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The Observation of Gravitational Waves from a Binary Black Hole Merger

Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models

Classical generalization of general relativity is considered as gravitational alternative for unified description of the early-time inflation with late-time cosmic acceleration. The structure and cosmological properties of number of modified theories, including traditional $F(R)$ and Hořava-Lifshitz $F(R)$ gravity, scalar-tensor theory, string-inspired and Gauss-Bonnet theory, non-local gravity, non-minimally coupled models, and power-counting renormalizable covariant gravity are discussed. Different representations and relations between such theories are investigated. It is shown that some versions of above theories may be consistent with local tests and may provide qualitatively reasonable unified description of inflation with dark energy epoch. The cosmological reconstruction of different modified gravities is made in great detail. It is demonstrated that eventually any given universe evolution may be reconstructed for the theories under consideration: the explicit reconstruction is applied to accelerating spatially-flat FRW universe. Special attention is paid to Lagrange multiplier constrained and conventional $F(R)$ gravities, for last theory the effective $\Lambda$CDM era and phantom-divide crossing acceleration are obtained. The occurrence of Big Rip and other finite-time future singularities in modified gravity is reviewed as well as its curing via the addition of higher-derivative gravitational invariants.

We consider $f(R,T)$ modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar $R$ and of the trace of the stress-energy tensor $T$. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Generally, the gravitational field equations depend on the nature of the matter source. The field equations of several particular models, corresponding to some explicit forms of the function $f(R,T)$, are also presented. An important case, which is analyzed in detail, is represented by scalar field models. We write down the action and briefly consider the cosmological implications of the $f(R,{T}^{\ensuremath{\phi}})$ models, where ${T}^{\ensuremath{\phi}}$ is the trace of the stress-energy tensor of a self-interacting scalar field. The equations of motion of the test particles are also obtained from a variational principle. The motion of massive test particles is nongeodesic, and takes place in the presence of an extra-force orthogonal to the four velocity. The Newtonian limit of the equation of motion is further analyzed. Finally, we provide a constraint on the magnitude of the extra acceleration by analyzing the perihelion precession of the planet Mercury in the framework of the present model.

$f(R,T)$ gravity

Foundations of Classical Electrodynamics

Bit-patterned media (BPM) for magnetic recording provides a route to thermally stable data recording at >1 Tb/in 2 and circumvents many of the challenges associated with extending conventional granular media technology. Instead of recording a bit on an ensemble of random grains, BPM comprises a well-ordered array of lithographically patterned isolated magnetic islands, each of which stores 1 bit. Fabrication of BPM is viewed as the greatest challenge for its commercialization. In this paper, we describe a BPM fabrication method that combines rotary-stage e-beam lithography, directed self-assembly of block copolymers, self-aligned double patterning, nanoimprint lithography, and ion milling to generate BPM based on CoCrPt alloy materials at densities up to 1.6 Td/in 2 . This combination of novel fabrication technologies achieves feature sizes of 2 (roughly equivalent to 1.3 Tb/in 2 ) demonstrate a raw error rate -2 , which is consistent with the recording system requirements of modern hard drives. Extendibility of BPM to higher densities and its eventual combination with energy-assisted recording are explored.

Bit-Patterned Magnetic Recording: Theory, Media Fabrication, and Recording Performance

Preface * Introduction * Part A--Mathematics: Some Exterior Calculus * Why Exterior Differential Forms? * A.1. Algebra * A.2. Exterior Calculus * A.3. Integration on a Manifold * Part B--Axioms of Classical Electrodynamics * B.1. Electric Charge Conservation * B.2. Lorentz Force Density * B.3. Magnetic Flux Conservation * B.4. Basic Classical Electrodynamics Summarized, Example * B.5. Electromagnetic Energy-Momentum Current and Action* Part C--More Mathematics * C.1. Linear Connection * C.2. Metric * Part D--The Maxwell--Lorentz Spacetime Relation * D.1. A Linear Relation Between H and F * D.2. Propagation of Electromagnetic Waves: Quartic Wave Surface * D.3. First Constraint: Electric/Magnetic Reciprocity * D.4. Second Constraint: Vanishing Skewon Field and Light Cone * D.5. Extracting the Metric by an Alternative Method * D.6. Fifth Axiom: Maxwell--Lorentz Spacetime Relation * Part E--Electrodynamic in Vacuum and in Matter * E.1. Standard Maxwell--Lorentz Theory in a Vacuum * E.2. Electrodynamic Spacetime Relations Beyond Locality and Linearity * E.3. Electrodynamics in Matter, Constitutive Law * Electrodynamics of Moving Continua * Outlook * References * Author Index * Subject Index

Foundations of Classical Electrodynamics: Charge, Flux, and Metric

In the gauge theory of gravity based on the Poincare group (the semidirect product of the Lorentz group and the spacetime translations) the mass (energy–momentum) and the spin are treated on an equal footing as the sources of the gravitational field. The corresponding spacetime manifold carries the Riemann–Cartan geometric structure with the nontrivial curvature and torsion. We describe some aspects of the classical Poincare gauge theory of gravity. Namely, the Lagrange–Noether formalism is presented in full generality, and the family of quadratic (in the curvature and the torsion) models is analyzed in detail. We discuss the special case of the spinless matter and demonstrate that Einstein's theory arises as a degenerate model in the class of the quadratic Poincare theories. Another central point is the overview of the so-called double duality method for constructing of the exact solutions of the classical field equations.

Poincare gauge gravity: Selected topics

The variational theory of an ideal spinning fluid is developed. This is described by original Weyssenhoff-Raabe tensors of spin and energy-momentum. Both neutral and charged fluids are considered, and the equations of motion and conservation laws for the Weyssenhoff neutral fluid in the Riemann-Cartan spacetime are discussed. The results are applied to the study of cosmological models with rotation, shear and expansion in the framework of the Einstein-Cartan theory of gravity.

https://iopscience.iop.org/article/10.1088/0264-9381/4/6/021/pdf

Yuri N. Obukhov

Papers

Foundations of Classical Electrodynamics

Bit-Patterned Magnetic Recording: Theory, Media Fabrication, and Recording Performance

Foundations of Classical Electrodynamics: Charge, Flux, and Metric

Poincare gauge gravity: Selected topics

The Weyssenhoff fluid in Einstein-Cartan theory