Karen Yagdjian
In this article we give sufficient conditions for the generalized Dirac operator to obey the incomplete Huygens principle, as well as necessary and sufficient conditions to obey the Huygens principle by the Dirac operator in the curved spacetime of the Friedmann-Lemaître-Robertson-Walker models of cosmology.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
In this article we give sufficient and necessary conditions for the validity of the Huygens' principle for the Dirac operator in the non-constant curvature spacetime of the Friedmann-Lemaître-Robertson-Walker models of cosmology. The Huygens' principle discussed for the equation of a particle with mass $m=0$ as well as a massive spin-1/2 particle (field) undergoing a red shift of its wavelength as the universe expands.
It is shown that there exist several ways to treat the quantum-mechanical Coulomb problem for a Dirac particle in flat Minkowski space with the help of the Heun differential equation, Fuchs's equation with four singular points. When extending the problem to curved spaces of constant curvature, Lobachevsky H_{3} and Rimann S_{3}, there arise 2-nd order differential equations of the Fuchs type with 6 singular points, a method to get relevant equations with five singular points has been elaborated.
In this short article, we non-perturbatively derive a recursive formula for the Green's function associated with finitely many point Dirac delta potentials in one dimension. We also extend this formula to the case for the Dirac delta potentials supported by regular curves embedded in two dimensional manifolds and for the Dirac delta potentials supported by two dimensional compact manifolds embedded in three dimensional manifolds. Finally, this formulation allows us to find the recursive formula of the Green's function for the point Dirac delta potentials in two and three dimensional Riemannian…
This is a survey of the author's recent work rather than a broad survey of the literature. The survey is concerned with the global in time solutions of the Cauchy problem for matter waves propagating in the curved spacetimes, which can be, in particular, modeled by cosmological models. We examine the global in time solutions of some class of semililear hyperbolic equations, such as the Klein-Gordon equation, which includes the Higgs boson equation in the Minkowski spacetime, de Sitter spacetime, and Einstein & de Sitter spacetime. The crucial tool for the obtaining those results is a new appro…
We consider Dirac equation in $(2+1)$ dimensional curved spacetime in the presence of a scalar potential. It is then shown that the zero energy states are degenerate and they can be obtained when the momentum $k_y$ in the $y$ direction satisfies certain constraints involving the mass parameter and the scalar potential coupling.
The Dirac equation in curved spacetimes is formulated using coordinate-free notation. A Lagrangean density which corresponds to the subject equation is presented. The subject equation is invariant under a local rotation of the coframe. The current is independent of the local orientation of the coframe and it is conserved. The subject equation has an equivalent formulation which uses the Christoffel gamma. The stress-energy tensor is calculated.
Differential Geometrical Methods for Deriving Dirac's Equation in Curved Spacetime to Account for the Presence of Matter
本文给出了弯曲时空中Dirac方程的微分几何推导方法。爱因斯坦的场方程以一种新颖的方式被应用;在最新的标准参考文献Birrell和Davies，1994 [1]中，推导弯曲时空中狄拉克方程的建议没有提到使用爱因斯坦的场方程。因此，到目前为止，关于狄拉克方程推导的文献还不能包括物质存在的表达式。这种缺乏与早期的出版物一致，包括Lichnerowicz着名的1964年期刊文章[3]，其中提出了第一个这样的推导，以及Dimock的1982年文章[2]。新的微分几何方法超越了以前的所有建议，这些建议只适用于没有物质的情况。这些微分几何方法导致了狄拉克方程在弯曲时空中的推导，适用于物质的存在或不存在。
In this work, we have obtained the solutions of the (1 + 1) dimensional Dirac equation on a gravitational background within the generalized uncertainty principle. We have shown that how minimal length parameters effect the Dirac particle in a spacetime described by conformally flat metric. Also, supersymmetric quantum mechanics is used both to factorize the Dirac Hamiltonians and obtain new metric functions. Finally, it is observed that the energy dependent potentials may be extended to the energy dependent metric functions.
We present the fundamental solutions for the spin-1/2 fields propagating in the spacetimes with power type expansion/contraction and the fundamental solution of the Cauchy problem for the Dirac equation. The derivation of these fundamental solutions is based on formulas for the solutions to the generalized Euler-Poisson-Darboux equation, which are obtained by the integral transform approach.
We write the Dirac equation in curved 4-dimensional Lorentzian spacetime using concepts from the analysis of partial differential equations as opposed to geometric concepts.
The Dirac wave function in a curved spacetime is usually defined as a quadruplet of scalar fields. It can alternatively be defined as a four-vector field. We describe these two representations in a common geometrical framework and we prove theorems that relate together the different representations and the different choices of connections. In particular, the standard Dirac equation in a curved spacetime, with any choice of the tetrad field, is equivalent to a particular realization of the Dirac equation for a vector wave function, in the same spacetime.
A Variational Principle for Block Operator Matrices and its Application to the Angular Part of the Dirac Operator in Curved Spacetime
在Kerr-Newman背景度规中与狄拉克方程的角部分相关联的算子是具有有界对角和无界非对角项的块算子矩阵。本文的目的是建立这类分块算子矩阵的一个变分原理，并导出角算子矩阵的上、下界。在最后一节中，这些解析界进行了比较，从文献中的数值。
One of the most important characteristics of light in flat spacetime is that it satisfies Huygens' principle: Initial data for the vacuum Maxwell equations evolves sharply along null (and not timelike) geodesics. In flat spacetime, there are no tails which linger behind expanding wavefronts. Tails generically do exist, however, if the background spacetime is curved. The only non-flat vacuum geometries where electromagnetic fields satisfy Huygens' principle are known to be those associated with gravitational plane waves. This paper investigates whether perturbations to the plane wave geometry i…
Heun-type solutions for the Dirac particle on the curved background of Minkowski space-times
研究光锥上Minkowski时空背景中的Dirac方程，通过径向耦合将方程组约化为二阶微分方程并得到Heun型解与能谱，结果也适用于磁场中的无自旋带电粒子。
A particular family of time- and space-dependent discrete-time quantum walks (QWs) is considered in one dimensional physical space. The continuous limit of these walks is defined through a new procedure and computed in full detail. In this limit, the walks coincide with the propagation of a massless Dirac fermion in an arbitrary gravitational field. A QW mimicking the radial propagation of a fermion outside and inside the event horizon of a Schwarzschild black hole is explicitly constructed and simulated numerically. Finally, the limiting procedure and the main result itself are carefully disc…
We study the notion of a Dirac operator in the framework of twist-deformed noncommutative geometry. We provide a number of well-motivated candidate constructions and propose a minimal set of axioms that a noncommutative Dirac operator should satisfy. These criteria turn out to be restrictive, but they do not fix a unique construction: two of our operators generally satisfy the axioms, and we provide an explicit example where they are inequivalent. For highly symmetric spacetimes with Drinfeld twists constructed from sufficiently many Killing vector fields, all of our operators coincide. For ge…
Dirac equation in curved spacetime: the role of local Fermi velocity
本文研究了带电载流子在存在局部费米速度的弯曲狄拉克材料中的运动，给出了纳米卷曲柱面几何中该物理量的显式参数化，并讨论了相关的物理效应与可观测性质。
The Dirac Hamiltonian in the (2+1) dimensional curved space-time has been studied with a metric for an expanding de Sitter space-time which is a two sphere. The spectrum and the exact solutions of the time dependent non-Hermitian and angle dependent Hamiltonians are obtained in terms of the Jacobi and Romanovski polynomials. Hermitian equivalent of the Hamiltonian obtained from the Dirac equation is discussed in the frame of pseudo-Hermiticity. Furthermore, pseudo-supersymmetric quantum mechanical techniques are expanded to a curved Dirac Hamiltonian and a partner curved Dirac Hamiltonian is g…
A Lagrangian theory giving rise to a version of the Dirac-Kahler equations on curved backgrounds is considered. The principal pieces are the general fields which have values in the algebra of the Dirac matrices and satisfy a Dirac-type equation. Their components are scalar, pseudo-scalar, vector, axial-vector fields and fields strength which satisfy an irreducible systems of first-order Dirac-Kahler equations having remarkable gauge and duality properties similar to those of the flat case. The vector and axial-vector fields are the physical potentials giving rise to the field strength while th…
We study the basic quantum mechanics for a fully general set of Dirac matrices in a curved spacetime by extending Pauli's method. We further extend this study to three versions of the Dirac equation: the standard (Dirac-Fock-Weyl or DFW) equation, and two alternative versions, both of which are based on the recently proposed linear tensor representations of the Dirac field (TRD). We begin with the current conservation: we show that the latter applies to any solution of the Dirac equation, iff the field of Dirac matrices $γ^μ$ satisfies a specific PDE. This equation is always satisfied for DFW …
One may ask whether the relations between energy and frequency and between momentum and wave vector, introduced for matter waves by de Broglie, are rigorously valid in the presence of gravity. In this paper, we show this to be true for Dirac equations in a background of gravitational and electromagnetic fields. We first transform any Dirac equation into an equivalent canonical form, sometimes used in particular cases to solve Dirac equations in a curved spacetime. This canonical form is needed to apply the Whitham Lagrangian method. The latter method, unlike the WKB method, places no restricti…
A common view is that generalization of a wave equation on Riemannian space-time is substantially determined by what a particle is - boson or fermion. As a rule, they say that tensor equations for bosons are extended in a simpler way then spinor equations for fermions. In that context, a very interesting problem is of extension a wave equation for Dirac--Kähler field (Ivanenko--Landau field was historically first term, also the term a vector field of general type was used). The article relates a generally covariant tensor formalism to a spinor one when these both are applied to description of …
We present a semiclassical analysis for Dirac fields on an arbitrary spacetime background and in the presence of a fixed electromagnetic field. Our approach is based on a Wentzel-Kramers-Brillouin approximation, and the results are analyzed at leading and next-to-leading order in the small expansion parameter $\hbar$. Taking into account the spin-orbit coupling between the internal and external degrees of freedom of wave packets, we derive effective ray equations with spin-dependent terms. These equations describe the gravitational spin Hall effect of localized Dirac wave packets. We treat bot…
The idea of wave mechanics leads naturally to assume the well-known relation $E=\hbar ω$ in the specific form $H=\hbar W$, where $H$ is the classical Hamiltonian of a particle and $W$ is the dispersion relation of the sought-for wave equation. We derive the expression of $H$ in a curved spacetime with an electromagnetic field. Then we derive the Dirac equation from factorizing the polynomial dispersion equation corresponding with $H$. Conversely, summarizing a recent work, we implement the geometrical optics approximation into a canonical form of the Dirac Lagrangian. Euler-Lagrange equations …
First-order symmetries of Dirac equation in curved background: a unified dynamical symmetry condition
结果表明，对于所有的维数和特征，在弯曲背景下，包括与Maxwell场相互作用的Dirac方程的最一般的一阶线性对称算子都以Killing-Yano（KY）形式给出.作为一般的规范不变条件，我们发现在所有的（伪）黎曼流形的KY-形式中，只有Clifford与Maxwell场可交换的形式才参与对称算符.它还证明了，与每个KY-形式参加的对称算子，可以定义一个二次函数的速度，这是一个测地线不变，以及一个常数的经典轨迹的运动。一些几何和物理意义的存在的KY-形式也阐明。
The Dirac equation in a curved spacetime depends on a field of coefficients (essentially the Dirac matrices), for which a continuum of different choices are possible. We study the conditions under which a change of the coefficient fields leads to an equivalent Hamiltonian operator H, or to an equivalent energy operator E. We do that for the standard version of the gravitational Dirac equation, and for two alternative equations based on the tensor representation of the Dirac fields. The latter equations may be defined when the spacetime is four-dimensional, noncompact, and admits a spinor struc…
Symmetries and supersymmetries of the Dirac operators in curved spacetimes
证明了任意维曲流形中Dirac算子的所有对称或超对称所涉及的主要几何对象是任意秩的Killing向量和Killing-Yano张量.一般理论的外部对称变换与通常的等距，指出这些离开标准狄拉克方程不变提供正确的自旋部分的群生成元。此外，分析了由协变常数Killing-Yano张量产生的新类型的对称性，这些张量实现了度量张量的某些平方根。这样一个Killing-Yano张量同时产生一个Dirac型算子和一个连接该算子与标准Dirac算子的单参数李群的生成元。这样，狄拉克算子通过与特定离散算子相关联的连续变换而相互关联。它表明，这种连续对称的群只能是U（1）或SU（2），作为（超）Kahler空间的那些，但即使在这些特殊几何的要求没有得到满足的情况下也会出现。在此基础上，详细介绍了欧氏Taub-NUT空间及其Dirac型算子，指出存在一个无限圈超代数充当闭动力学代数结构的角色。作为最后一个主题，我们去考虑闵可夫斯基时空的狄拉克型算子的性质。
Nuclearity, Local Quasiequivalence and Split Property for Dirac Quantum Fields in Curved Spacetime
我们证明了整体双曲时空上的自由Dirac量子场具有以下结构性质：（a）自由Dirac场代数上的任意两个准自由Hadamard态是局部准等价的，（b）任何准自由Hadamard态的表示都具有分裂性质;（c）如果基础时空是静态的，那么满足核性条件，即，与一个可扩展子系统（"盒子“）相关的自由能与盒子的体积有线性关系，并且对于大的温度$T$，自由能的变化类似于$\propto T^{s+1}$，其中$s+1$是时空的维数。
We show that the exterior algebra bundle over a curved spacetime can be used as framework in which both the Dirac and the Einstein equations can be obtained. These equations and their coupling follow from the variational principle applied to a Lagrangian constructed from natural geometric invariants. We also briefly indicate how other forces can potentially be incorporated within this geometric framework.
A Quantum Weak Energy Inequality for Dirac fields in curved spacetime
众所周知，量子场违反了广义相对论的弱能量条件：在任何给定点处的重整化能量密度作为量子态的函数从下到上都是无界的。与此相反，对于标量场和电磁场，已经表明，沿类时曲线的能量密度的加权平均值满足“量子弱能量不等式"，它构成了这些量的下限。以前，狄拉克QWEI只在二维时空中的无质量场中得到。在本文中，我们建立了一般四维整体双曲时空上的Dirac和Majorana质量场$m\ge 0$的QWEI，平均沿着任意光滑类时曲线关于任何一个大类光滑紧支撑的正权重。我们的证明利用了Hadamard态类的微局域特征，其能量密度可以用点分裂来定义。
We give a local integral formula, valid on general curved space-times, for the characteristic Cauchy problem for the Dirac equation with arbitrary spin using the method developed by Friedlander in his book "the wave equation on a curved spacetime" (1975). The results obtained by Penrose in the flat case in "Null hypersurface initial data for classical fields of arbitrary spin for general relativity" (Gen. Rel. Grav 1980) are recovered directly. It is expected that this method can be used to obtain sharp estimates for the characteristic Cauchy problem for the Dirac equation.
Hidden symmetries and Killing tensors on curved spaces
研究了Killing张量对应的高阶对称性。指出了Killing-Yano张量与非标准超对称的密切关系。在曲空间上的Dirac理论中，Killing-Yano张量生成Dirac型算子，这些算子涉及到有趣的代数结构，如动力代数，甚至无限维代数或超代数。一般结果适用于现代研究中出现的时空。在四维欧氏Taub-NUT空间上给出了Dirac型算子的无限维超代数，它可以看作是一个扭圈代数。研究了具有混合Sasakian结构的空间的共形Killing-Yano张量的存在性。
Singularity structure of the two point function of the free Dirac field on a globally hyperbolic spacetime
本文介绍了微局域分析技术在弯曲时空中自由量子场论的阿达玛态研究中的成功应用。回顾了Hadamard态自由Klein-Gordon场两点函数波前集的计算，并计算了弯曲时空中自由Dirac场Hadamard两点函数的偏振集.
Integrable Schrödinger operators with magnetic fields: factorisation method on curved surfaces
研究了具有非平凡度量的二维曲面$M^2$上带磁场的薛定谔算子的因式分解方法.这就引出了这类算子的新的可积例子，并使人们对一些经典问题如狄拉克磁问题和朗道问题有了新的认识。从因子分解链的运营商的全球几何方面和相关的频谱特性进行了详细讨论。我们还考虑了曲面上的Laplace变换，推广了S.P.Novikov和作者之一在平坦情形下引入的具有两个可积水平的薛定谔算子类。
A Covariant Chiral-Hydrodynamic Formulation of the Dirac Equation in Curved Spacetime
通过引入两个独立零向量解耦左右手征分量，发展出狄拉克场的完全协变手征流体动力学表述，在无挠广义相对论中自然隔离自旋-轨道耦合并证明自旋-引力耦合消失，在史瓦西几何中得到精确径向解并计算准束缚态谱、准正则模频率和灰体因子，通过建立精确能量平衡方程从手征流守恒导出霍金辐射通量。
In a Minkowski spacetime, one may transform the Dirac wave function under the spin group, as one transforms coordinates under the Poincaré group. This is not an option in a curved spacetime. Therefore, in the equation proposed independently by Fock and Weyl, the four complex components of the Dirac wave function transform as scalars under a general coordinate transformation. Recent work has shown that a covariant complex four-vector representation is also possible. Using notions of vector bundle theory, we describe these two representations in a unified framework. We prove theorems that relate…
Quantum Fisher Information in Curved Spacetime: Dirac Particles in Noisy Channels around a Schwarzschild Black Hole
研究 Schwarzschild 黑洞弯曲时空中三量子比特 Dirac 系统经 SGAD、GAD 与 AD 信道后的 QFI，发现强压缩可抑制 Hawking 温度影响并减缓退相干。
Magnetic Dirac operator in strips submitted to strong magnetic fields
该研究针对带无穷质量边界条件的弯曲条形区域上的强磁场磁狄拉克算子，给出了本质谱与离散谱的精确估计，并得到离散谱非空的充分条件，丰富了狄拉克算子谱理论的相关结果。
First, the present work is concerned with generalising constructions and results in quantum field theory on curved spacetimes from the well-known case of the Klein-Gordon field to Dirac fields. To this end, the enlarged algebra of observables of the Dirac field is constructed in the algebraic framework. This algebra contains normal-ordered Wick polynomials in particular, and an extended analysis of one of its elements, the stress-energy tensor, is performed. Based on detailed calculations of the Hadamard coefficients of the Dirac field, it is found that a construction of a stress-energy tensor…
Dirac operators and field equations of the gravitational field and matter fields
本文提出将观测者纳入自然规律表述的新观点，据此在弯曲时空引入满足洛伦兹不变性和哈密顿关系的狄拉克算子，并构建结合引力场与物质场的场方程，指出强引力场下观测效应不可避免。
We study perturbations of the flat geometry of the noncommutative two-dimensional torus T^2_θ(with irrational θ). They are described by spectral triples (A_θ, \H, D), with the Dirac operator D, which is a differential operator with coefficients in the commutant of the (smooth) algebra A_θof T_θ. We show, up to the second order in perturbation, that the zeta-function at 0 vanishes and so the Gauss-Bonnet theorem holds. We also calculate first two terms of the perturbative expansion of the corresponding local scalar curvature.
When a two-dimensional curved surface is conceived as a limiting case of a curved shell of equal thickness d, where the limit d\rightarrow0 is then taken, the well-known geometric potential is induced by the kinetic energy operator, in fact by the second order partial derivatives. Applying this confining procedure to the momentum operator, in fact to the first order partial derivatives, we find the so-called geometric momentum instead. This momentum is compatible with the Dirac's canonical quantization theory on system with second-class constraints. The distribution amplitudes of the geometric…
The source-free Maxwell action is invariant under electric-magnetic duality rotations in arbitrary spacetimes. This leads to a conserved classical Noether charge. We show that this conservation law is broken at the quantum level in presence of a background classical gravitational field with a non-trivial Chern-Pontryagin invariant, in a parallel way to the chiral anomaly for massless Dirac fermions. Among the physical consequences, the net polarization of the quantum electromagnetic field is not conserved.
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。