Title: Doppelganger defects Show Chinese title

Title: 双生缺陷

Abstract: We study k-defects - topological defects in theories with more than two derivatives and second-order equations of motion - and describe some striking ways in which these defects both resemble and differ from their analogues in canonical scalar field theories. We show that, for some models, the homotopy structure of the vacuum manifold is insufficient to establish the existence of k-defects, in contrast to the canonical case. These results also constrain certain families of DBI instanton solutions in the 4-dimensional effective theory. We then describe a class of k-defect solutions, which we dub doppelgangers, that precisely match the field profile and energy density of their canonical scalar field theory counterparts. We give a complete characterization of Lagrangians which admit doppelganger domain walls. By numerically computing the fluctuation eigenmodes about domain wall solutions, we find different spectra for doppelgangers and canonical walls, allowing us to distinguish between k-defects and the canonical walls they mimic. We search for doppelgangers for cosmic strings by numerically constructing solutions of DBI and canonical scalar field theories. Despite investigating several examples, we are unable to find doppelganger cosmic strings, hence the existence of doppelgangers for defects with codimension >1 remains an open question. Show Chinese abstract

Abstract: 我们研究k缺陷——在具有超过两个导数和二阶运动方程的理论中的拓扑缺陷——并描述这些缺陷与规范标量场理论中的对应物既相似又不同的显著方式。 我们证明，在某些模型中，真空流形的同伦结构不足以确定k缺陷的存在，这与规范情况形成对比。 这些结果还限制了四维有效理论中某些DBI瞬子解家族。 然后我们描述了一类称为双生体的k缺陷解，它们精确地匹配其规范标量场理论对应物的场分布和能量密度。 我们给出了承认双生体域墙的拉格朗日量的完整特征描述。 通过数值计算域墙解附近的涨落本征模式，我们发现双生体和规范壁有不同的谱，使我们能够区分k缺陷和它们所模仿的规范壁。 我们通过数值构造DBI和规范标量场理论的解来寻找宇宙弦的双生体。 尽管研究了多个例子，但我们无法找到双生体宇宙弦，因此对于余维数大于1的缺陷是否存在双生体仍然是一个开放问题。