In any medium there are fluctuations due to temperature or due to the quantum nature of its
constituents. If a material body is immersed into such a medium, its shape and the properties …

Decoherence inevitably happens when a quantum state is exposed to its environment,
which can affect quantum critical points (QCPs) in a nontrivial way. As was pointed out in the …

Defects in conformal field theory (CFT) are of significant theoretical and experimental
importance. The presence of defects theoretically enriches the structure of the CFT, but at …

A bstract We study a surface defect in the free and critical O (N) vector models, defined by
adding a quadratic perturbation localized on a two-dimensional subspace of the d …

A bstract We study mass-type surface defects in a free scalar and Wilson-Fisher (WF) O (N)
theories. We obtain exact results for the free scalar defect, including its RG flow and defect …

It is known that the classical O (N) model in dimension d> 3 at its bulk critical point admits
three boundary universality classes: the ordinary, the extra-ordinary and the special. For the …

A bstract Coleman's theorem states that continuous internal symmetries cannot be
spontaneously broken in two-dimensional quantum field theories (QFTs). In this work we …

Some quantum critical states cannot be smoothly deformed into each other without either
crossing some multicritical points or explicitly breaking certain symmetries even if they …

This paper studies the critical behavior of the 3d classical $\mathrm {O}(N) $ model with a
boundary. Recently, one of us established that upon treating $ N $ as a continuous variable …

We study a class of symmetry protected topological (SPT) phases under various types of
decoherence, which can drive a pure SPT state into a mixed state. We demonstrate that the …