We discuss a string model where a conformal four-dimensional N=2 gauge theory receives corrections to its gauge kinetic functions from "stringy" instantons. These contributions are explicitly evaluated by exploiting the localization properties of the integral over the stringy instanton moduli space. The model we consider corresponds to a setup with D7/D3-branes in type I' theory compactified on T4/Z2 x T2, and possesses a perturbatively computable heterotic dual. In the heteoric side the corrections to the quadratic gauge couplings are provided by a 1-loop threshold computation and, under the duality map, match precisely the first few stringy instanton effects in the type I' setup. This agreement represents a very non-trivial test of our approach to the exotic instanton calculus.
We show that when sterile Majorana neutrino masses are generated non-perturbatively through instantonic interactions in certain classes of string compactifications (e.g. Type IIA orientifold models with intersecting D-branes), then the eigenvalue spectrum for the tree-level mass term $M_p$ can be within the preferred range of the Neutrino Option resolution to the electroweak (EW) hierarchy and neutrino mass problems of the Standard Model, i.e. $M_p \sim$ PeV. This mechanism holds without tuning for a broad range of string scales, thereby motivating a novel class of string-completed Neutrino Op…
本文对D1-D5膜系统的规范线性西格玛模型在一个解析的A_1奇点上进行了精确计算。这是通过超对称局部化爆破的两个球。我们证明了在C^2/Z_2的吹落极限下，配分函数约化为Nekrasov配分函数来计算瞬子模空间的等变体积.对于有限的半径，我们得到了一个世界片瞬子修正塔，我们确定与ADHM模空间的等变Gromov-Witten不变量。我们表明，这些修正可以编码在变形的Seiberg-Witten prepotential。从数学的观点来看，所研究的D1-D5系统表现出双重性质：D1-膜的观点捕获了Givental形式主义中ADHM瞬子模空间的等变量子上同调，而D5-膜的观点与P^1 x C^2的高阶等变Donaldson-Thomas不变量有关。
我们提出了一个弦机制产生狄拉克中微子质量的D-瞬子在实验相关的质量尺度没有微调。在具有相交D 6-膜的IIA型弦论中，我们阐明了这种耦合出现的具体条件，并基于Z_2 x Z '_2定向折叠紧化提供了一类超对称局域SU（5）大统一模型，其中在实验观测的质量区域中，D2-膜瞬子可以产生微扰不存在的Dirac中微子质量，而Majorana质量仍然不存在，因此，提供了一个有趣的机制，小中微子质量的起源，由于非微扰弦效应。
We study how the microstates of BPS sectors in string theory are organized in the dual $U(N)$ gauge theory. The microstates take the form of a coherent sum of stacks of branes and their open/closed string excitations. We propose a prescription to holographically construct the indices of string/brane configurations by analyzing the modifications of determinant operators in gauge theory. The string/brane configurations should be interpreted in the tensionless limit, but their indices are well-defined at finite $N$. In various examples, we provide evidence that a sum, of the giant graviton-type r…
We study the first-order in $α'$ corrections to 4-charge black holes (with the Reissner-Nordström black hole as a particular example) beyond the near-horizon limit in the Heterotic Superstring effective action framework. The higher-curvature terms behave as delocalized sources in the equations of motion and in the Bianchi identity of the 3-form. For some charges, this introduces a shift between their values measured at the horizon and asymptotically. Some of these corrections and their associated charge shifts, but not all of them, can be canceled using appropriate SU$(2)$ instantons for the h…
We study the global structure of vacua of heterotic strings compactified on orbifolds $T^4/Z_N$ (N=2,3) in the presence of heterotic 5-branes. Gauge symmetry breaking associated with orbifold is described by instantons in the field theory. Phase transition between small instantons and heterotic 5-branes provides top-down, stringy account to the spectrum and modular invariance condition. Also it takes us from one vacuum to another by emitting and absorbing instantons. This means that many vacua with different gauge theory are in fact connected and are inherited from perturbative vacua. It follo…
G. Física CAB-CNEA, Centro Atómico Bariloche（CAB-CNEA 物理组，巴里洛切原子中心）；Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（国家科学研究委员会）；Instituto Balseiro, Universidad Nacional de Cuyo (UNCUYO)（巴尔塞罗研究所，门多萨国立大学）
