# Quantum density anomaly in optically trapped ultracold gases

## TL;DR

This paper demonstrates a density anomaly in ultracold quantum gases modeled by the Bose-Hubbard Model, revealing a first quantum state anomaly linked to zero point entropies and phase transitions, with implications for water-like behaviors.

## Contribution

It is the first to identify a density anomaly in a quantum state within ultracold gases, connecting quantum phase transitions to anomalous density behavior.

## Key findings

- Density increases with temperature at fixed pressure in the superfluid phase.
- First observation of a density anomaly in a quantum state.
- Links between zero point entropies, phase transitions, and density anomalies.

## Abstract

We show that the Bose-Hubbard Model exhibits an increase in density with temperature at fixed pressure in the regular fluid regime and in the superfluid phase. The anomaly at the Bose-Einstein condensate is the first density anomaly observed in a quantum state. We propose that the mechanism underlying both the normal phase and the superfluid phase anomalies is related to zero point entropies and ground state phase transitions. A connection with the typical experimental scales and setups is also addressed. This key finding opens a new pathway for theoretical and experimental studies of water-like anomalies in the area of ultracold quantum gases.