高温超导体玻色子超导弦理论及其应用

本文用 u(?)×u(1) 场论描述高温氧化物超导体.求得了玻色子超导弦场方程的孤子解,并把理论结果应用于讨论 Cu-O 型超导体的一些特性.     

宇宙弦的弦张力

由宇宙弦的理想气体热力学模型出发,用鞍点近似方法,导出了宇宙弦的弦张力表达式.     

弦论小史（三）

我在《超弦史话》一开始就描述了弦论第二次革命开始的情形,多年后的现在回顾起来,也还是充满刺激。弦论第二次革命发端于1994年中的两篇文章：威滕和塞伯格（Nathan Seiberg）关于超对称规范理论的文章,以及胡尔（Christopher Hull）和汤森（Paul Townsend）关于弦论中的所谓U对偶的文章。在美国,第一篇影响的效应是即时的,甚至纽约时报都在第一时间报道了这个进展。一时之间,网上的物理文库充满了关于超对称场论的文章。与威滕和塞伯格工作的遭遇相反,起初没有太多人重视胡尔和汤森的工作。     

重力对弦振动特征频率的影响

本文从非均匀弦波动方程出发探讨重力对弦振 动特征频率的影响．讨论了两种不同边界条件下竖直 均质弦驻波特征频率与其重量之间的关系，给出了在 弦重量远小于其张力时两端固定的竖直均质弦驻波特 征频率修正项的解析表达式．     

四维杂化弦

利用十维N-S玻色弦和四维费米弦杂化,我们给出了四维杂化弦.其内部规范对称群为[SU(2)]⁶.它的基态包含有四维时空的超引力多重态及四维超杨-Mills规范多重态.四维杂化弦具有超对称、无快子态及洛仑兹不变等特性.     

用频谱分析法研究弦振动实验

用频谱分析法,通过计算机实测实验研究弦的线性自由振动和线性受迫振动规律,得到了弦振动的基频和谐频的量值关系,与理论计算结果一致.该实验方法有利于加深学生对机械振动和机械波理论的深入理解,以及掌握用频谱分析法测量物体振动频谱的方法.     

弦振动实验装置的改进

弦振动实验装置的改进郑稷（重庆师范专科学校６３２１６８）弦振动实验是力学实验中一个重要而典型的实验．该实验的主要内容是研究弦振动的基频与弦长（其他条件不变）和基频与张力（其他条件不变）的关系．实验方法有两种：（１）采用振动频率固定的振动体，通过改变弦...     

M_d×G时空Spinning弦的协变二次量子化

本文给出了M_d×G时空BRSSS Spinning弦模型的BRS荷Q_B.由BRS荷的幂零性质确定了该模型的临界维数和参数α_0~(NS)与α_0~R;并利用BRS荷构造了BRSSS Spinning弦的BRS不变的自由开弦场论.我们发现,在这个模型中,只有在取Abel群时,才能使超对称性和BRS不变性共存.最后,我们写出了作用量的零质量部分,它含有带群指标的规范场.     

竖直悬挂弦上横波的波速

解析地计算了竖直悬挂弦上横波的相速度,与直接应用张力均匀弦上的波速公式计算结果一致,从而证实了张力均匀弦上的波速公式对张力不均匀弦适用.     

振动弦的“色散”实验研究

研究了有界弦横向强迫振动时弦上波速的色散现象.实验测量结果表明:由弦的张力和线密度决定的弦上的波速(T/ρ)~1/2不一定是常量,在一定的条件下,弦的波速会随着弦驻波的波长长度(弦长)改变而变化.     

Covariant open string field theory on multiple Dp-branes

We study covariant open bosonic string field theories on multiple Dp-branes by using the deformed cubic string field theory, which is equivalent to string field theory in the proper-time gauge. Constructing the Fock space representations of the three-string vertex and the four-string vertex on multiple Dp-branes, we obtain the field theoretical effective action in the zero-slope limit. On multiple D0-branes, the effective action reduces to the Banks-Fishler-Shenker-Susskind(BFSS) matrix model. We also discuss the relation between open string field theory on multiple D-instantons in the zero-slope limit and the Ishibashi-Kawai-Kitazawa-Tsuchiya(IKKT) matrix model.The covariant open string field theory on multiple Dp-branes could be useful to study the non-perturbative properties of quantum field theories in(p+1)-dimensions in the framework of the string theory. The non-zero-slope corrections may be evaluated systematically by using covariant string field theory.     

Homotopy Classification of Bosonic String Field Theory

We prove the decomposition theorem for the loop homotopy Lie algebra of quantum closed string field theory and use it to show that closed string field theory is unique up to gauge transformations on a given string background and given S-matrix. For the theory of open and closed strings we use results in open-closed homotopy algebra to show that the space of inequivalent open string field theories is isomorphic to the space of classical closed string backgrounds. As a further application of the open-closed homotopy algebra, we show that string field theory is background independent and locally unique in a very precise sense. Finally, we discuss topological string theory in the framework of homotopy algebras and find a generalized correspondence between closed strings and open string field theories.     

The Effective Theory of Strings

We show that the Nambu–Goto string, and its higher dimensional generalizations, can be quantized, in the sense of an effective theory, in any dimension of the target space. The crucial point is to consider expansions around classical string configurations. We are using tools from perturbative algebraic quantum field theory, quantum field theory on curved spacetimes, and the Batalin–Vilkovisky formalism. Our model has some similarities with the Lüscher–Weisz string, but we allow for arbitrary classical background string configurations and keep the diffeomorphism invariance.     

M-theory: Strings,duality and branes

String theory is an attempt to combine all of the known physical forces into a single unified framework. A powerful new type of duality symmetry has recently been discovered in string theory which has led to important breakthroughs. What were previously considered to be five distinct string theories are now known to be different aspects of an underlying structure called M-theory. In addition to strings, extended objects of higher dimension or 'branes', play a key role. We review these developments and discuss the impact that they are having on quantum field theory and the quantum properties of black holes.     

The T-dual symmetries of a bosonic string

We investigate whether the symmetry transformations of a bosonic string are connected by T-duality. We start with a standard closed string theory. We continue with a modified open string theory, modified to preserve the symmetry transformations possessed by the closed string theory. Because the string theory is conformally invariant world-sheet field theory, in order to find the transformations which preserve the physics, one has to demand the isomorphism between the conformal field theories corresponding to the initial and the transformed field configurations. We find the symmetry transformations corresponding to the similarity transformation of the energy-momentum tensor, and find that their generators are T-dual. Particularly, we find that the general coordinate and local gauge transformations are T-dual, so we conclude that T-duality in addition to the well-known exchanges, transforms symmetries of the initial and its T-dual theory into each other.     

Tachyon condensation and open string field theory

We perform canonical quantization of open string on a unstable D-brane in the background of tachyon condensation. Evaluating the Polyakov path-integral on a strip, we obtain a field theoretical propagator in the open string theory. As condensation occurs the string field theory is continuously deformed. At the infrared fixed point of condensation, the open string field on the unstable D-brane transmutes to that on the lower-dimensional D-brane with the correct D-brane tension.     

Two-Dimensional Topological Strings Revisited

The topological string of the type A with a two-dimensional target space is studied, an explicit formula for the string partition function is found and the target space field theory reproducing this partition function is proposed. This field theory has an infinite set of additional deformations overlooked by the standard definition of the topological string. It can be in turn coupled to gravity, thereby realizing the “worldsheets for worldsheets” idea. We also exhibit the wave function nature of the string partition function and suggest a new relation to quantum integrable systems.     

Loop variables and gauge invariant exact renormalization group equations for (open) string theory

An exact renormalization group equation is written down for the world sheet theory describing the bosonic open string in general backgrounds. Loop variable techniques are used to make the equation gauge invariant. This is worked out explicitly up to level 3. The equation is quadratic in the fields and can be viewed as a proposal for a string field theory equation. As in the earlier loop variable approach, the theory has one extra space dimension and mass is obtained by dimensional reduction. Being based on the sigma model RG, it is background independent. It is intriguing that in contrast to BRST string field theory, the gauge transformations are not modified by the interactions up to the level calculated. The interactions can be written in terms of gauge invariant field strengths for the massive higher spin fields and the non-zero mass is essential for this. This is reminiscent of Abelian Born–Infeld action (along with derivative corrections) for the massless vector field, which is also written in terms of the field strength.     

A covariant open bosonic string field theory including the endpoint and middlepoint interaction

Extending the usual endpoint and midpoint interactions, we introduce numerous kinds of interactions, labelled by a parameter λ and obtain a non-commutative and associative string field algebra by adding up all interactions. With this algebra we develop a covariant open bosonic string field theory, which reduces to Witten's open bosonic string field theory under a special string length choice.