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1.
Let M be a symplectic manifold with a Hamiltonian circle action with isolated fixed points. We prove that σ (M) = b0(M) − b2(M) + b4(M) − b6(M) + … where σ (M) is the signature of M and bi(M) is the ith Betti number of M. 相似文献
2.
Helga Baum 《Journal of Geometry and Physics》1987,4(4):503-522
Let
(P) be the moduli space of irreducible connections of a G-principal bundle P over a closed Riemannian spin manifold M. Let DA be the Dirac operator of M coupled to a connection A of P and f a smooth function on M. We consider a smooth variation A(u) of A with tangent vector ω and denote Tω:=
(DA(u)−f) (u=0. The coefficients of the asymptotic expansion of trace (Tω · e-t(DA−f)2) near t=0 define 1-forms a(k)f, K=0, 1, 2, … on
(P). In this paper we calculate aa(0)f, a(1)f, a(2)f and study some of their properties. For instance using the 1-form a(2)f for suitable functions f we obtain a foliation of codimension 5 of the space of G-instantons of S4. 相似文献
3.
Jens Chr. Larsen 《Journal of Geometry and Physics》2003,45(3-4):252-266
This paper proves that the Riemannian distance function is maximal in the class of distance functions associated with the Riemannian metric tensor.on a complete Riemannian surface (M,g) with small curvature, small curvature change and injectivity radius +∞. Here piM and γv is the maximal geodesic with initial velocity v and 0<t1<<tm. 相似文献
Secondly, it is proven that there exists a unique minimum of
4.
Partha Guha 《Journal of Geometry and Physics》2003,46(3-4):231-242
It is known that the Korteweg–de Vries (KdV) equation is a geodesic flow of an L2 metric on the Bott–Virasoro group. This can also be interpreted as a flow on the space of projective connections on S1. The space of differential operators Δ(n)=∂n+u2∂n−2++un form the space of extended or generalized projective connections. If a projective connection is factorizable Δ(n)=(∂−((n+1)/2−1)p1)(∂+(n−1)/2pn) with respect to quasi primary fields pi’s, then these fields satisfy ∑i=1n((n+1)/2−i)pi=0. In this paper we discuss the factorization of projective connection in terms of affine connections. It is shown that the Burgers equation and derivative non-linear Schrödinger (DNLS) equation or the Kaup–Newell equation is the Euler–Arnold flow on the space of affine connections. 相似文献
5.
On nonanalytic solitary waves formed by a nonlinear dispersion 总被引:7,自引:0,他引:7
Philip Rosenau 《Physics letters. A》1997,230(5-6):305-318
We study the prototypical, genuinely nonlinear, K(m, n) equation, ut ± a(um)x + (un)xxx = 0, a = const, which exhibits a number of remarkable dispersive effects. In particular, the distinguished subclass wherein m = n + 2 is transformed into a new, purely dispersive equation free of convection. In addition to compactons, the K(m, n) can support both kinks and solitons with an infinite slope(s), periodic waves and dark solitons with cusp(s) all being manifestations of nonlinear dispersion in action. For n < 0 the enhanced dispersion at the tail may generate algebraically decaying patterns. 相似文献
6.
G. Triscone M. S. Chae M. C. de Andrade M. B. Maple 《Physica C: Superconductivity and its Applications》1997,290(3-4):188-205
We have investigated the reversible mixed-state magnetization M of three lanthanum substituted Bi1.95Sr2.05−xLaxCuOy (Bi-2201) ceramic samples having different critical temperatures Tc ranging from 20.0 to 35.5 K. As for the Bi2Sr2CaCu2O8+δ (Bi-2212) phase, we found that anisotropy of Bi-2201 is large. A manifestation of this anisotropy is the field independent magnetization M* observed at a temperature T*. In the framework of the London model, and including thermal fluctuations of vortices, we found for the temperature dependence of the penetration depth λab(T) = λab(0)[1 − (T/Tc0)n]−1/2, with n 1.7 and λab (T = 0) 4000 Å. The estimated upper critical fields μ0Hc2,c are of the order of 10 T. We observe a peculiar negative slope M/T at low temperature and sufficiently high external magnetic field. This feature seems to be a characteristic of the Bi-2201 phase. However, we do not know whether it is associated with the superconducting mixed-state. A small amount of magnetic impurities could also be responsible for this behavior. Finally, the behavior of the reversible magnetization of the Bi-2201 samples investigated, which are situated at the optimal and in the overdoped region, did not indicate any unusual temperature dependence for the upper critical field Hc2,c. 相似文献
7.
It is shown that each one-parameter subgroup of SL(2,R) gives rise to a local correspondence theorem between suitably generic solutions of arbitrary scalar equations describing pseudo-spherical surfaces. Thus, if appropriate genericity conditions are satisfied, there exist local transformations between any two solutions of scalar equations arising as integrability conditions of sl(2,R)-valued linear problems.
A complete characterization of evolution equations ut=K(x,t,u,ux,…,uxk) which are of strictly pseudo-spherical type is also provided. 相似文献
8.
In the Minimal Supersymmetric Standard Model (MSSM), the masses of the charged Higgs boson (H±) and the CP-odd scalar (A) are related by MH+2=MA2+mW2. Furthermore, because the coupling of W−–A–H+ is fixed by gauge interaction, the tree level production rate of
depends only on one supersymmetry parameter—the mass (MA) of A. We show that to a good approximation this conclusion also holds at the one-loop level. Consequently, this process can be used to distinguish MSSM from its alternatives (such as a general two-Higgs-doublet model) by verifying the above mass relation, and to test the prediction of the MSSM on the product of the decay branching ratios of A and H± in terms of only one single parameter—MA. 相似文献
9.
10.
系统地研究了核磁共振碳谱(13C NMR)与化学位移规律及其定量构谱关系(QSSR).本文研究了一组多元素分子子图指数矢量(VMSG),并发现它与烷烃化学位移和(CCSA)有很好线性相关性.采用多元线性回归(MVLR)进行准确估计与预测,结果良好. 相似文献
11.
考虑一类演化方程ut=au∂2k+1(其中a是常数,u∂2k+1=∂2k+1u/∂x2k+1,k=1,2……)的有限差分解法。构造了两类具有高稳定性的显式差分格式。并用引入耗散项的方法建立了两类半显式差分格式,它们是无条件稳定的且可显式地进行计算。 相似文献
12.
Juan A. Navarro Gonzalez Juan B. Sancho de Salas 《Journal of Geometry and Physics》2003,44(4):595-622
We consider a smooth one-parameter family of four-dimensional manifolds X,≥0, each one endowed with a covariant metric g. It is assumed that g is a Lorentz metric for each >0, i.e., the signature of g is (+,−,−,−) for >0, while the limit metric g0 on X0 is assumed to be degenerated of rank 1, i.e., the signature of g0 is (+,0,0,0). We characterize when the limit manifold X0 inherits the geometric structure of a Newtonian gravitation. The limit manifold X0 is a Newtonian gravitation if and only if there exist the limits of the Levi-Civita connection , the curvature operator
and the contravariant Einstein tensor G2 as →0. Moreover, the existence of these limits is characterized in terms of the Taylor expansion of the family {g} with respect to the parameter . 相似文献
13.
Anomalous magnetotransport phenomena have been observed in θ-(BEDT-TTF)2I3 crystals at temperatures below 15 K. The magnetoresistance M : (1) is a linear function of the magnetic field H, (2) is not affected by the angle between the electric current and the magnetic field, (3) but depends on the magnetic field orientation with respect to the crystal axis. Magnetoresistance is expressed as M = (aH2a + bH2b + cH2c)0-3/2/H in terms of H = (Ha, Hb, Hc), the zero field resistivity 0, and parameters a, b, and c which are independent of temperature and magnetic field. We have found that b a > c. Magnetoresistance up to 40 is observed for H = 7T along the b-axis at T = 1.5K. 相似文献
14.
K. Fox 《Journal of Quantitative Spectroscopy & Radiative Transfer》1970,10(12):1335-1342
A rigorous calculation of the quantum-mechanical rotational partition function for tetrahedral XY4 molecules yields Qr = (
)(2IY + 1)4π
-
exp(/4), where IY is the spin of the Y nucleus, and ≡ Bhc/kT. This result is accurate to 1 per cent or better for all values of B and T such that <
. 相似文献
15.
We study the scaling properties of noise reduced Eden clusters in three and four dimensions for variant B in the strip geometry. We find that the width W for large times behaves as a(s)g(L/sd−1), where L is the width of the strip, s the noise reduction parameter, d the dimension of space, and a(s) a decreasing function of s, g is a scaling function with the property g(u)→1/2 as u→0 and g(u)ux as u→∞, where χ is the roughness exponent. This scaling result leads to a new way of determining χ. In 3 dimensions, our numerical values for χ support a recent conjecture by Kim and Kosterlitz: χ = 2/(d + 2), and contradict all the former analytical conjectures. In 4 dimensions, we cannot distinguish between the conjectures of Kim and Kosterlitz and the conjecture of Wolf and Kertész, because large crossovers and finite size effects make the measurement of the exponents difficult. 相似文献
16.
17.
A. I. Tovstolytkin N. A. Belous I. V. Lezhnenko 《Journal of magnetism and magnetic materials》1994,130(1-3):293-296
We present here the detailed analysis of the magnetic behavior of the Co0.53Ga0.47 alloy, especially at temperatures above the freezing temperature Tf = 10 K. Low field static magnetization measurements were performed by using the SQUID magnetometer in the temperature range 5–65 K and magnetic fields up to 100 Oe. The temperature dependence of the field cooled susceptibility πFC(T) at T > Tf has an anomaly, which is displayed in the double change of the curvature near Ts = 24 K. The data of magnetization MFC in an external field H lie on a universal curve MFC(H/T) at temperatures Tf < T < Ts. The plots of π-1FC(T) and non-linear magnetic susceptibility πnlFC(T-3) are linear lines in the temperature range Tf−Ts. The strong deviation of π-1FC(T) and πnlFC(T-3) from straight line, taking place at T Ts, indicates that Ts is an upper temperature limit of the classical superparamagnetic behavior with the constant cluster moment. The results suggest that such phenomena may be fairly universal for spin glasses. 相似文献
18.
We study planar random surfaces on a hypercubic lattice in two and three dimensions by Monte Carlo techniques. Our data are consistent with the formula n0(A;C) Ab0A, where n0(A;C) is the number of planar random surfaces with area A and boundary C. We find b0 = −1.4 ± 0.2, = 5.31 ± 0.03 (for d = 2) and b0 = −1.5 ± 0.2, = 7.13 ± 0.05 (for d = 3). The values of b0 disagree with those obtained from the Polyakov string model. 相似文献
19.
MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究 下载免费PDF全文
研究MC与Mn+1ACn(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构Mn+1ACn稳定性的内在原因和设计新型Mn+1ACn结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与Mn+1ACn 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成Mn+1ACn. 与M2PC和M2SC 相比, M2AlC和M2SiC可以更为容易地被分离成二维 M2C结构.
关键词:
MAX相结构
第一性原理
电子结构
过渡金属碳化物 相似文献
20.
Let
be the action integral on a semiriemannian manifold (
, g) defined on the space of the curves z : [0, 1] →
joining two given points z0 and z1. The critical points of ƒ are the geodesics joining z0 and z1. Let s ε [0, 1]. We study the behavior, in dependence of s, of the eigenvalues of the Hessian form of ƒ evaluated at z, restricted to the interval [0, s]. A formula for the derivative of the eigenvalues is given and some applications are shown. 相似文献