Brownian Loops, Layering Fields and Imaginary Gaussian Multiplicative Chaos

Federico Camia, Alberto Gandolfi, Giovanni Peccati, Tulasi Ram Reddy

Research output: Contribution to journalArticlepeer-review


We study fields reminiscent of vertex operators built from the Brownian loop soup in the limit as the loop soup intensity tends to infinity. More precisely, following Camia et al. (Nucl Phys B 902:483–507, 2016), we take a (massless or massive) Brownian loop soup in a planar domain and assign a random sign to each loop. We then consider random fields defined by taking, at every point of the domain, the exponential of a purely imaginary constant times the sum of the signs associated to the loops that wind around that point. For domains conformally equivalent to a disk, the sum diverges logarithmically due to the small loops, but we show that a suitable renormalization procedure allows to define the fields in an appropriate Sobolev space. Subsequently, we let the intensity of the loop soup tend to infinity and prove that these vertex-like fields tend to a conformally covariant random field which can be expressed as an explicit functional of the imaginary Gaussian multiplicative chaos with covariance kernel given by the Brownian loop measure. Besides using properties of the Brownian loop soup and the Brownian loop measure, a main tool in our analysis is an explicit Wiener–Itô chaos expansion of linear functionals of vertex-like fields. Our methods apply to other variants of the model in which, for example, Brownian loops are replaced by disks.

Original languageEnglish (US)
Pages (from-to)889-945
Number of pages57
JournalCommunications In Mathematical Physics
Issue number3
StatePublished - Feb 2021

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Mathematical Physics


Dive into the research topics of 'Brownian Loops, Layering Fields and Imaginary Gaussian Multiplicative Chaos'. Together they form a unique fingerprint.

Cite this