Covariant Effective Action for Quantum Particle with Coordinate-Dependent Mass

Covariant BRST Quantization of Closed Strings in the PP-Wave Background

We canonically quantize closed string theory in the pp-wave background with a non-zero flux of the three-form field strength by using the covariant BRST operator formalism. In this canonical quantization, we completely construct new covariant free-mode representations, for which it is particularly important to take account of the commutation relations of the zero mode of the light-cone string coordinate X^{-} with other modes. All covariant string coordinates are composed of the free-modes. Moreover, employing these covariant string coordinates for the energy-momentum tensor, we calculate the …

标量场在有边界的流形上的非局部有效作用的协变外在曲率展开

Covariant extrinsic curvature expansion of the nonlocal effective action for a massless scalar field on a manifold with boundary

本文研究了定义在平坦流形上有弯曲边界的无质量标量场的非局部有效作用，通过热核方法推导了外在曲率张量到二次项的协变展开，扩展了Monge-patch嵌入的结果，并应用于计算二维和三维振荡变形环和球的粒子产生率。

量子协变导数

Quantum covariant derivative

本文提出量子协变导数，证明其规范与坐标协变性及与量子几何张量的相容性，并据此建立不变的绝热微扰理论以计算非线性绝热响应。

Quantum Action Principle for Covariant Systems. Bosonic string

A new form of covariant quantum theory based on a quantum version of the action principle is considered for the case of a free bosonic string. The central idea of the new approach is to delay conditions of stationarity of the classical action with respect to Lagrangian multipliers up to the quantum level where delayed conditions of stationarity are imposed on a quantum action. Physical states of the ordinary covariant quantum theory are replaced by well defined stationary states as those which obey quantum action principle. The stationary states have well defined energies.

Variance of the Quantum Coordinates of an Event

We study the variances of the coordinates of an event considered as quantum observables in a Poincare' covariant theory. The starting point is their description in terms of a covariant positive-operator-valued measure on the Minkowski space-time. Besides the usual uncertainty relations, we find stronger inequalities involving the mass and the centre-of-mass angular momentum of the object that defines the event. We suggest that these inequalities may help to clarify some of the arguments which have been given in favour of a gravitational quantum limit to the accuracy of time and space measureme…

The Choi-Jamiolkowski isomorphism and covariant quantum channels

A generalization of the Choi-Jamiolkowski isomorphism for completely positive maps between operator algebras is introduced. Particular emphasis is placed on the case of normal unital completely positive maps defined between von Neumann algebras. This generalization is applied especially to the study of maps which are covariant under actions of a symmetry group. We highlight with the example of, e.g., phase-shift-covariant quantum channels the ease of this method in particular in the case of a compact symmetry group. We also discuss the case of channels which are covariant under actions of the …