Discrete Time Crystals in the Absence of Manifest Symmetries or Disorder in Open Quantum Systems.

We establish a link between metastability and a discrete time-crystalline phase in a periodically driven open quantum system. The mechanism we highlight requires neither the system to display any microscopic symmetry nor the presence of disorder, but relies instead on the emergence of a metastable regime. We investigate this in detail in an open quantum spin system, which is a canonical model for the exploration of collective phenomena in strongly interacting dissipative Rydberg gases. Here, a semiclassical approach reveals the emergence of a robust discrete time-crystalline phase in the thermodynamic limit in which metastability, dissipation, and interparticle interactions play a crucial role. We perform numerical simulations in order to investigate the dependence on the range of interactions, from all to all to short ranged, and the scaling with system size of the lifetime of the time crystal.

A terahertz-driven non-equilibrium phase transition in a room temperature atomic vapour.

There are few demonstrated examples of phase transitions that may be driven directly by terahertz frequency electric fields, and those that are known require field strengths exceeding 1 MV cm-1. Here we report a non-equilibrium phase transition driven by a weak (≪1 V cm-1), continuous-wave terahertz electric field. The system consists of room temperature caesium vapour under continuous optical excitation to a high-lying Rydberg state, which is resonantly coupled to a nearby level by the terahertz electric field. We use a simple model to understand the underlying physical behaviour, and we demonstrate two protocols to exploit the phase transition as a narrowband terahertz detector: the first with a fast (20 µs) non-linear response to nano-Watts of incident radiation, and the second with a linearised response and effective noise equivalent power ≤1 pW Hz-1/2. The work opens the door to a class of terahertz devices controlled with low-field intensities and operating in a room temperature environment.

Emergent kinetic constraints, ergodicity breaking, and cooperative dynamics in noisy quantum systems.

Kinetically constrained spin systems play an important role in understanding key properties of the dynamics of slowly relaxing materials, such as glasses. Recent experimental studies have revealed that manifest kinetic constraints govern the evolution of strongly interacting gases of highly excited atoms in a noisy environment. Motivated by this development we explore which types of kinetically constrained dynamics can generally emerge in quantum spin systems subject to strong noise and show how, in this framework, constraints are accompanied by conservation laws. We discuss an experimentally realizable case of a lattice gas, where the interplay between those and the geometry of the lattice leads to collective behavior and time-scale separation even at infinite temperature. This is in contrast to models of glass-forming substances which typically rely on low temperatures and the consequent suppression of thermal activation.

Hemangioma of the hand.

The authors describe the anatomopathological and clinical findings of 24 cases of benign hemangioma of the hand. The instrumental methods used to diagnose hemangioma are discussed, and MRI imaging is given particular importance in the preoperative evaluation of the site, size, extent, and relationship with the surrounding tissues and any multiple locations of the vascular tumor. This evaluation is essential to perform a wide resection of the tumor, which is the only means of avoiding recurrence. After an average follow-up of 33 months (14-54) recurrence was observed in 7% of the cases treated.

Transdermal scopolamine use in the control of narcotic-induced nausea.

Nausea affects from 40% to 70% of cancer patients who received narcotics to manage their pain. This occurs more frequently when they are ambulatory than when they are recumbent and may be the result of narcotic-enhanced labyrinthine sensitivity to motion. Scopolamine has previously been found to be an effective antiemetic for motion sickness. In a prospective pilot study, 9 (69%) of 13 cancer patients experienced rapid relief of their narcotic-induced nausea when they used Scopolamine Transderm-V patches alone. Only two patients experienced side effects with the scopolamine, and in one patient, the side effects may have been dose related. Although tolerance to the increased vestibular sensitivity may occur, this was not universal. Further prospective trials are necessary to establish whether transdermal scopolamine is useful in controlling the narcotic-induced nausea experienced by cancer patients.