We consider the decay of a false vacuum in circumstances where the methods suggested by Coleman run into difficulties. We find that in these cases quantum fluctuations play a crucial role. Namely, they naturally induce both an ultraviolet and infrared cutoff scales, determined by the parameters of the classical solution, beyond which this solution cannot be trusted anymore. This leads to the appearance of a broad class of new $O(4)$ invariant instantons, which would have been singular in the absence of an ultraviolet cutoff. We apply our results to a case where the potential is unbounded from below in a linear way and in particular show how the problem of small instantons is resolved by taking into account the inevitable quantum fluctuations.
We identify an infinite class of unbounded potentials for which the Coleman instantons do not exist in D-dimensional spacetime. For such potentials, the decay of a false vacuum is described by the new instantons introduced in [5,6,4]. For each spacetime dimension D, we also construct the two different classes of potentials for which the instanton equations are exactly solvable.
We develop a new method for estimating the decay probability of the false vacuum via regularized instantons. Namely, we consider the case where the potential is either unbounded from below or the second minimum corresponding to the true vacuum has a depth exceeding the height of the potential barrier. In this case, the materialized bubbles dominating the vacuum decay naturally have a thick wall and the thin-wall approximation is not applicable. We prove that in such a case the main contribution to the action determining the decay probability comes from the part of the solution for which the po…
For a scalar theory whose classical scale invariance is broken by quantum effects, we compute self-consistent bounce solutions and Green's functions. Deriving analytic expressions, we find that the latter are similar to the Green's functions in the archetypal thin-wall model for tunneling between quasi-degenerate vacua. The eigenmodes and eigenspectra are, however, very different. Large infrared effects from the modes of low angular momentum $j=0$ and $j=1$, which include the approximate dilatational modes for $j=0$, are dealt with by a resummation of one-loop effects. For a parametric example…
Local Chirality of Low-Lying Dirac Eigenmodes and the Instanton Liquid Model
讨论了用低阶Dirac本征模探测QCD中拓扑荷涨落局域结构的原因，指出这些模中局域手征取向概率分布的定性双峰行为是必要的，但不足以使类瞬子涨落占优势.本文报道了格点间距为a~0.04 fm ~ a~0.12 fm的Wilson规范背景中重叠Dirac算符的结果，发现导致分布双峰的局域结构的大小和密度与瞬子液体模型的假设不一致。更一般地说，我们的结果表明，拓扑荷的真空涨落在QCD中并不有效地由局部量子化（整数值）块控制。
We study the Harper-Hofstadter Hamiltonian and its corresponding non-perturbative butterfly spectrum. The problem is algebraically solvable whenever the magnetic flux is a rational multiple of $2π$. For such values of the magnetic flux, the theory allows a formulation with two Bloch or $θ$-angles. We treat the problem by the path integral formulation, and show that the spectrum receives instanton corrections. Instantons as well as their one loop fluctuation determinants are found explicitly and the finding is matched with the numerical band width of the butterfly spectrum. We extend the analys…
In quantum chromodynamics (QCD), the role which topologically non-trivial configurations play in splitting the singlet pseudo-Goldstone meson, the $η^\prime$, from the octet is familiar. In addition, such configurations contribute to other processes which violate the axial $U(1)_A$ symmetry. While the nature of topological fluctuations in the confined phase is still unsettled, at temperatures well above that for the chiral phase transition, they can be described by a dilute gas of instantons. We show that instantons of arbitrary topological charge $Q$ generate anomalous interactions between $2…
We investigate the role of gauge and gravitational instantons in the context of the Swampland program. Our focus is on the global symmetry breaking they induce, especially in the presence of fermions. We first recall and make more precise the description of the dilute instanton gas through a 3-form gauge theory. In this language, the familiar suppression of instanton effects by light fermions can be understood as the decoupling of the 3-form. Even if all fermions remain massive, such decoupling may occur on the basis of an explicitly unbroken but anomalous global symmetry in the fermionic sect…
Three-loop Correction to the Instanton Density. II. The Sine-Gordon potential
在这篇关于经典瞬子组态附近量子涨落的第二篇论文中，参见{ \em Phys. Rev. D \bf 92}，025046（2015）和arXiv：1501.03993，我们关注另一个研究得很好的量子力学问题，一维Sine-Gordon势（Mathieu势）。利用量子场论中的工具--瞬子背景下的费曼图，我们计算了三圈量级的隧穿振幅（瞬子密度）。结果证实了最近由G. V. Dunne和M.Ünsal，{ \it Phys. Rev. \bf D 89}，105009（2014）从复苏的角度。在双势阱的情况下，我们发现，最大的贡献是由来自雅可比矩阵的图。我们再次观察到，在三圈的情况下，个别费曼图包含无理数的贡献，而它们的和则不包含。
We revisit the problem of charged string pair creation in a constant external electric field. The string states are massive and creation of pairs from the vacuum is a tunnelling process, analogous to the Schwinger process where charged particle-anti-particle pairs are created by an electric field. We find the instantons in the worldsheet sigma model which are responsible for the tunnelling events. We evaluate the sigma model partition function in the multi-instanton sector in the WKB approximation which keeps the classical action and integrates the quadratic fluctuations about the solution. We…
We study the backreaction of superhorizon fluctuations of a light quantum scalar field on a classical de Sitter geometry by means of the Wilsonian renormalisation group. This allows us to treat the gravitationally amplified fluctuations in a nonperturbative manner and to analytically follow the induced renormalisation flow of the spacetime curvature as long wavelength modes are progressively integrated out. Unbounded loop corrections in the deep infrared are eventually screened by nonperturbative effects which stabilise the geometry.
Quantum systems with multiple degenerate classical harmonic minima exhibit new non-perturbative phenomena which are not present for the double-well and periodic potentials. The simplest characteristic example of this family is the triple-well potential. Despite the fact that instantons are exact semiclassical solutions with finite and minimal action, they do not contribute to the energy spectrum at leading order in the semiclassical analysis. This is because the instanton fluctuation prefactor vanishes, which can be interpreted as the action becoming infinite quantum mechanically. Instead, the…
The semi-classical expansion and resurgence in gauge theories: new perturbative, instanton, bion, and renormalon effects
本文利用费米子周期边界条件下的圆紧化方法，研究了所有规范群伴随费米子的四维规范理论的微扰和非微扰动力学.有新的规范现象。我们表明，在微扰理论的所有订单，许多规范群Higgsed的规范完整性周围的圆的产品的阿贝尔和nonabel规范群因子。在非微扰情况下，有费米子零模的夸克瞬子和两种夸克反夸克分子，称为生物子。一种类型是“磁生物子”，它携带净磁荷，并引起规范波动的质量间隙。另一种类型是磁中性的“中性生物子”，对它们的理解需要将量子力学中的多瞬子技术--我们称之为博戈莫尼-津恩-贾斯汀（BZJ）处方--推广到紧致化场论。应用于生物-反生物拓扑分子的BZJ处方预测了Borel平面的正实轴上的奇点（即，在微扰理论中，大阶求和的发散），它比领先的4-d BPST瞬子-反瞬子奇点更接近原点N倍，其中N是规范群的秩。的bion-反bion奇异的位置，从而定性类似的4-D IR renormalon奇异，我们猜想，它们是连续相关的紧化半径的变化。利用跨级数和Ecalle的复活理论，我们证明了一类允许半经典展开的场论的非微扰连续统定义是可能的。
