Geodesic continued fractions and LLL

We discuss a proposal for a continued fraction-like algorithm to determine simultaneous rational approximations to d$d$ real numbers _α1,…,_αd${\alpha }_1,\dots ,{\alpha }_d$. It combines an algorithm of Hermite and Lagarias with ideas from LLL-reduction. We dynamically LLL-reduce a quadratic form with parameter t$t$ as t↓0$t\downarrow 0$. Suggestions in this direction have been made several times over in the literature, e.g. Chevallier (2013) [4] or Bosma and Smeets (2013) [2]. The new idea in this paper is that checking the LLL-conditions consists of solving linear equations in t$t$.     

Electromagnetic momentum conservation in media

That static electric and magnetic fields can store momentum may be perplexing, but is necessary to ensure total conservation of momentum. Simple situations in which such field momentum is transferred to nearby bodies and point charges have often been considered for pedagogical purposes, normally assuming vacuum surroundings. If dielectric media are involved, however, the analysis becomes more delicate, not least since one encounters the electromagnetic energy–momentum problem in matter, the ‘Abraham–Minkowski enigma’, of what the momentum is of a photon in matter. We analyze the momentum balance in three nontrivial examples obeying azimuthal symmetry, showing how the momentum conservation is satisfied as the magnetic field decays and momentum is transferred to bodies present. In the last of the examples, that of point charge outside a dielectric sphere in an infinite magnetic field, we find that not all of the field momentum is transferred to the nearby bodies; a part of the momentum appears to vanish as momentum flux towards infinity. We discuss this and other surprising observations which can be attributed to the assumption of magnetic fields of infinite extent. We emphasize how formal arguments of conserved quantities cannot determine which energy–momentum tensor is more “correct”, and each of our conservation checks may be performed equally well in the Minkowski or Abraham framework.     

唐高宗朝“僧道致拜君亲”的论争与龙朔修格

关于高宗龙朔二年“僧道致拜君亲”之争议,以往研究者虽指出其事与高宗、武则天政治的关系,认为此事反映现实礼法冲突和法律思想,却较少具体事例予以证明。研究从龙朔修格的角度提供补充,说明《显庆礼》与龙朔修格的联系及礼法意义,从而指出“僧道致拜君亲”的讨论是龙朔礼法改革中的一项,不仅与武则天主持政事有关,也证实了她本人将佛教理念作为其家族信仰和立朝之支撑,以及追求帝、后权力平等的意向。不同参加者的意向则进一步证明此项论争与现实政治的关联。     

DISTORTION THEOREMS FOR BIHOLOMORPHIC CONVEX MAPPINGS ON BOUNDED CONVEX CIRCULAR DOMAINS

1.TwoDifferentDistortionTheoremsVariousdistortiontheoremsforfamiliesofunivalentfunctionshavebeenstudiedsinceasearlyas1907whenK5bediscoveredhis"Verzerrungssatz",thedistortiontheoremfortheclassofunivalentfunctionsdefinedontheunitdiskillthecomplexplaneC.LetfiCC"beadomainandf(z)=(fi(z),.',m(z))beabiholomorphicmappingonfiwhichmapsfitoC".Therearemanycounter-examplestoshowthatIdetJj(z)landJI(z)Jj(z)'havenofiniteupperboundandnonon--zerolowerbound,whereJf(z)istheJacobianoffatpointz.LetfiCC"bea…     

Locally Farkas–Minkowski Systems in Convex Semi-Infinite Programming

A pair of constraint qualifications in convex semi-infinite programming, namely the locally Farkas–Minkowski constraint qualification and generalized Slater constraint qualification, are studied in the paper. We analyze the relationship between them, as well as the behavior of the so-called active and sup-active mappings, accounting for the tightness of the constraint system at each point of the variables space. The generalized Slater constraint qualification guarantees a regular behavior of the supremum function (defined as supremum of the infinitely many functions involved in the constraint system), giving rise to the well-known Valadier formula.     

TVS-锥度量空间中的统计收敛

本文研究TVS-锥度量空间中的统计收敛以及TVS-锥度量空间的统计完备性.令（X,E,P,d）表示一个TVS-锥度量空间.利用定义在有序Hausdorff拓扑向量空间E上的Minkowski函数ρ,证明了在X上存在一个通常意义下的度量d_ρ,使得X中的序列（x_n）在锥度量d意义下统计收敛到x ∈ X,当且仅当（x_n）在度量d_ρ意义下统计收敛到x.基于此,我们证明了任意一个TVS-锥统计Cauchy序列是几乎处处TVS-锥Cauchy序列,还证明了任意一个TVS-锥统计收敛的序列是几乎处处TVS-锥收敛的.从而,TVS-锥度量空间（X,d）是d-完备的,当且仅当它是d-统计完备的.基于以上结论,通常度量空间中统计收敛的许多性质都可以平行地推广到锥度量空间中统计收敛的情形.     

Quaternionic analysis, representation theory and physics

We develop quaternionic analysis using as a guiding principle representation theory of various real forms of the conformal group. We first review the Cauchy-Fueter and Poisson formulas and explain their representation theoretic meaning. The requirement of unitarity of representations leads us to the extensions of these formulas in the Minkowski space, which can be viewed as another real form of quaternions. Representation theory also suggests a quaternionic version of the Cauchy formula for the second order pole. Remarkably, the derivative appearing in the complex case is replaced by the Maxwell equations in the quaternionic counterpart. We also uncover the connection between quaternionic analysis and various structures in quantum mechanics and quantum field theory, such as the spectrum of the hydrogen atom, polarization of vacuum, one-loop Feynman integrals. We also make some further conjectures. The main goal of this and our subsequent paper is to revive quaternionic analysis and to show profound relations between quaternionic analysis, representation theory and four-dimensional physics.     

A geometric inequality on mixed volumes

We develop some geometric inequality for a kind of generalized convex set. The integral of (n – 2)-th mean curvature of the generalized convex set, the mixed volume of the convex hull of the set, and a reference convex set are involved in the inequality.Partially supported by grants from Kosef and BSRI-95-1419.     

The Minkowski problem for polytopes

The traditional solution to the Minkowski problem for polytopes involves two steps. First, the existence of a polytope satisfying given boundary data is demonstrated. In the second step, the uniqueness of that polytope (up to translation) is then shown to follow from the equality conditions of Minkowski's inequality, a generalized isoperimetric inequality for mixed volumes that is typically proved in a separate context. In this article we adapt the classical argument to prove both the existence theorem of Minkowski and his mixed volume inequality simultaneously, thereby providing a new proof of Minkowski's inequality that demonstrates the equiprimordial relationship between these two fundamental theorems of convex geometry.     

Spacelike hypersurfaces with constant higher order mean curvature in Minkowski space–time

In this paper, we develop a series of general integral formulae for compact spacelike hypersurfaces with hyperplanar boundary in the (n+1)-dimensional Minkowski space–time . As an application of them, we prove that the only compact spacelike hypersurfaces in having constant higher order mean curvature and spherical boundary are the hyperplanar balls (with zero higher order mean curvature) and the hyperbolic caps (with nonzero constant higher order mean curvature). This extends previous results obtained by the first author, jointly with Pastor, for the case of constant mean curvature [J. Geom. Phys. 28 (1998) 85] and the case of constant scalar curvature [Ann. Global Anal. Geom. 18 (2000) 75].