The many-body physics at quantum phase transitions shows a subtle interplay between
quantum and thermal fluctuations, emerging in the low-temperature limit. In this review, we …

We review phase-space techniques based on the Wigner representation that provide an
approximate description of dilute ultra-cold Bose gases. In this approach the quantum field …

Phase transitions are ubiquitous in our three-dimensional world. By contrast, most
conventional transitions do not occur in infinite uniform low-dimensional systems because of …

The collective behaviour of a many-body system near a continuous phase transition is
insensitive to the details of its microscopic physics; for example, thermodynamic observables …

The condensation of fermion pairs lies at the heart of superfluidity. However, for strongly
correlated systems with reduced dimensionality the mechanisms of pairing and …

We present experimental results on a Bose gas in a quasi-2D geometry near the Berezinskii,
Kosterlitz, and Thouless (BKT) transition temperature. By measuring the density profile after …

We give in this lecture an introduction to the physics of two-dimensional (2d) Bose gases.
We first discuss the properties of uniform, infinite 2d Bose fluids at non-zero temperature T …

Using in situ measurements on a quasi-two-dimensional, harmonically trapped Rb 87 gas,
we infer various equations of state for the equivalent homogeneous fluid. From the …

In complementary images of coordinate-space and momentum-space density in a trapped
2D Bose<? format?> gas, we observe the emergence of presuperfluid behavior. As phase …

Quantum criticality emerges when a many-body system is in the proximity of a continuous
phase transition that is driven by quantum fluctuations. In the quantum critical regime, exotic …