# Posts tagged *Physics*

Despite being forbidden in equilibrium, spontaneous breaking of time translation symmetry can occur in periodically driven, Floquet systems with discrete time-translation symmetry. The period of the resulting discrete time crystal is quantized to an integer multiple of the drive period, arising from a combination of collective synchronization and many body localization. Here, we consider a simple model for a one-dimensional discrete time crystal which explicitly reveals the rigidity of the emergent oscillations as the drive is varied. We numerically map out its phase diagram and compute the properties of the dynamical phase transition where the time crystal melts into a trivial Floquet insulator. Moreover, we demonstrate that the model can be realized with current experimental technologies and propose a blueprint based upon a one dimensional chain of trapped ions. Using experimental parameters (featuring long-range interactions), we identify the phase boundaries of the ion-time-crystal and propose a measurable signature of the symmetry breaking phase transition.

via http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.030401

Normal crystals have an atomic structure that repeats in space - just like the carbon lattice of a diamond. But, just like a ruby or a diamond, they’re motionless because they’re in equilibrium in their ground state. But time crystals have a structure that repeats in time, not just in space. And it keep oscillating in its ground state. Imagine it like jelly - when you tap it, it repeatedly jiggles. The same thing happens in time crystals, but the big difference here is that the motion occurs without any energy. A time crystal is like constantly oscillating jelly in its natural, ground state, and that’s what makes it a whole new form of matter - non-equilibrium matter. It’s incapable of sitting still.

via http://www.sciencealert.com/scientists-have-just-announced-a-brand-new-form-of-matter-time-crystals

So much for classical objects and time travel. But what would happen if a quantum particle entered a closed time-like curve? In the early 90s, the physicist David Deutsch showed that not only is this possible but that it can only happen in a way that does not allow superluminal signalling. So quantum mechanics plays havoc with causality but in a way that is consistent with relativity and so prevents grandfather-type paradoxes. Deutsch’s result has extraordinary implications. It implies that closed time-like curves can be used to solve NP-complete problems in polynomial time and to violate Heisenberg’s uncertainty principle.

via https://medium.com/the-physics-arxiv-blog/the-quantum-experiment-that-simulates-a-time-machine–185a7cc9bd11

For the last ten years you’ve been told that the LHC must see some new physics besides the Higgs because otherwise nature isn’t “natural” – a technical term invented to describe the degree of numerical coincidence of a theory. I’ve been laughed at when I explained that I don’t buy into naturalness because it’s a philosophical criterion, not a scientific one. But on that matter I got the last laugh: Nature, it turns out, doesn’t like to be told what’s presumably natural. Now that the diphoton bump is gone, we’ve entered what has become known as the “nightmare scenario” for the LHC: The Higgs and nothing else. Many particle physicists thought of this as the worst possible outcome. It has left them without guidance, lost in a thicket of rapidly multiplying models. Without some new physics, they have nothing to work with that they haven’t already had for 50 years, no new input that can tell them in which direction to look for the ultimate goal of unification and/or quantum gravity. That the LHC hasn’t seen evidence for new physics is to me a clear signal that we’ve been doing something wrong, that our experience from constructing the standard model is no longer a promising direction to continue. We’ve maneuvered ourselves into a dead end by relying on aesthetic guidance to decide which experiments are the most promising. I hope that this latest null result will send a clear message that you can’t trust the judgement of scientists whose future funding depends on their continued optimism. Things can only get better.

via http://backreaction.blogspot.be/2016/08/the-lhc-nightmare-scenario-has-come-true.html?m=1