We study the first order form of the NS string sigma model allowing for worldsheet couplings corresponding on the target space to a bi-vector, a two-form and an inverse metric. Lifting the topological sector of this action to three dimensions produces several Wess-Zumino like terms which encode the bi-vector generalization of the Courant bracket. This bracket may be familiar to physicists through the (H_{ijk},F_{ij}^{k},Q_i^{jk},R^{ijk}) notation for non-geometric backgrounds introduced by Shelton-Taylor-Wecht. The non-geometricity of the string theory in encoded in the global properties of the bi-vector, when the bi-vector is a section then the string theory is geometric. Another interesting situation emerges when one considers membrane actions which are not equivalent to string theories on the boundary of the membrane. Such a situation arises when one attempts to describe the so-called R-space (the third T-dual of a T^3 with H_3 flux). This model appears to be, at least classically, described by a membrane sigma model, not a string theory. Examples of geometric backgrounds with bi-vector couplings and non-vanishing Q-coefficients are provided by gauged WZW models.
This paper is devoted to the canonical analysis of non-linear sigma model that describes motion of non-relativistic string on stringy Newton-Cartan background. We determine structure of constraints of this string and compare resulting Hamiltonian with previous proposal of non-relativistic string on Newton-Cartan background.
We continue the study of nonrelativistic string theory in background fields. Nonrelativistic string theory is described by a nonlinear sigma model that maps a relativistic worldsheet to a non-Lorentzian and non-Riemannian target space geometry, which is known to be string Newton-Cartan geometry. We develop the covariant background field method in this non-Riemannian geometry. We apply this background field method to compute the beta-functions of the nonlinear sigma model that describes nonrelativistic string theory on a string Newton-Cartan geometry background, in presence of a Kalb-Ramond two…
We study the worldsheet theory of bosonic string from the point of view of the BV formalism. We explicitly describe the derived Poisson structure which arizes when we expand the Master Action near a Lagrangian submanifold. The BV formalism allows us to clarify the mechanism of holomorphic factorization of string amplitudes.
On Open String Sigma-Model and Noncommutative Gauge Fields
我们考虑开弦西格玛模型中的普通和非对易Dirac Born Infeld理论。首先，我们提出了一个重整化方案，混合点分裂正则化，直接导致Seiberg-Witten描述，包括他们的两种形式。我们还表明，这样的形式出现在标准重整化方案只是通过一些自由改变变量。其次，我们提出了一个在经典水平上具有非对易规范不变性的Wilson因子，然后在一个已知的保持非对易规范不变性的重整化方案中计算了西格玛模型的配分函数。结果，我们找到了非对易的Yang-Mills作用。
Strings as Multi-Particle States of Quantum Sigma-Models
本文研究了O（2n）sigma模型中的量子Bethe不等式方程，考虑到它在S^{2n-1} x R_t空间弦量子化中的应用，其中粒子间的相互作用由Zamolodchikovs的S-矩阵给出.对于有限数量的粒子，系统看起来像一个非齐次可积的O（2n）自旋链。类似于OSp（2 m +n| 2 m）共形σ模型，在大粒子密度的极限下，我们再现了经典弦的有限间隙Kazakov-Marshakov-Minahan-Zarembo解，并将其推广到Green-Schwarz-Metsaev-Tseytlin超弦的S^5 x R_t扇区.我们还再现了一些量子效应：BMN极限和量子均匀自旋链，类似于描述单圈N=4超Yang-Mills理论的玻色子扇区.我们讨论了这些贝特方程推广到超弦σ模型的前景。
Heterotic String Sigma Models: Discrete Light Cone Quantization and Its Current-Current Deformation
University of Groningen（格罗宁根大学）；National Institute of Physics, University of the Philippines（菲律宾大学国家物理研究所）；Universidad de Murcia（穆尔西亚大学）；KTH Royal Institute of Technology and Stockholm University（瑞典皇家理工学院和斯德哥尔摩大学）
Beta Function of k Deformed AdS_5 x S^5 String Theory
我们计算了与q=exp（i pi/k）的量子群相关联的k个变形西格玛模型的世界片上可能的边缘耦合的单圈β函数.这包括玻色子主手征模型和对称空间西格玛模型，也包括k变形半对称空间西格玛模型，它描述了AdS_5 x S^5变形的弦。世界片西格玛模型是规范WZW模型对PSU（2，2）超群的电流-电流变形|4）k级。在弦论中，由于PSU（2，2）的Killing形式为零，β函数为零|4）这是另一个证明k变形理论定义了相容的弦论的证据。
We study a semi-local Abelian Higgs sigma model with $\mathbb{CP}^2$-valued scalar fields coupled to gravity. We establish the conditions needed for self-duality in this system and obtain cosmic strings, both of self-dual character and out of the self-dual point, in the reference chart of $\mathbb{CP}^2$. In any of the other two charts of a minimum atlas, the transition functions break the global $SU(2)$ symmetry to the Abelian subgroup $e^{i σ^3 α}$. In this context, using the transition functions a new self-dual structure can be constructed, which defines a second species of cosmic strings. …
We detail the construction of the exceptional sigma model, which describes a string propagating in the "extended spacetime" of exceptional field theory. This is to U-duality as the doubled sigma model is to T-duality. Symmetry specifies the Weyl-invariant Lagrangian uniquely and we show how it reduces to the correct 10-dimensional string Lagrangians. We also consider the inclusion of a Fradkin-Tseytlin (or generalised dilaton) coupling as well as a reformulation with dynamical tension.
