The Unruh Fest: A Celebration in Honour of Bill Unruh's 70th Birthday
Due to the linearity of the field equations and the resulting bilinear structure of the Hamiltonian, quantum radiation effects such as black hole evaporation or particle creation in an expanding universe are typically described as (squeezing) processes where particles are created in pairs.
Here, we address the following question: given a mode (e.g., wave-packet) corresponding to a created particle (e.g., as part of Hawking radiation), what is its partner, i.e., the other particle of the pair?
Can high energy physics can be simulated by low-energy, nonrelativistic, many-body systems, such as ultracold atoms? Ultracold atomic systems lack the type of symmetries and dynamical properties of high energy physics models: in particular, they do not manifest local gauge invariance nor Lorentz invariance, which are crucial properties of the quantum field theories which are the building blocks of the standard model of elementary particles.
I will sketch a few interesting phenomena involving ideal plasmas, including helicity conservation, frozen flux, the Blandford-Znajek mechanism, and self-confined Poynting jets, using the language of differential forms.
This year marks the 40’th anniversary of the Unruh effect as described at the first Marcel Grossmann meeting in 1975. We revisit it with emphasis on the observability issue which might be a concern at first sight, since the linear acceleration needed to reach a temperature 1 K is of order 10^20 m/s^2 . We close the talk by emphasizing that the Unruh effect does not require any verification beyond that of relativistic free field theory itself. The Unruh effect lives among us.
The quantum Zeno effect is often very controversial in the context of consciousness problems.
Frequent direct measurements of a quantum system freeze its time evolution.
Then what happes if an observer continuously watches a Schrodinger's cat from the start of the experiment?
Naively this looks like a yes-no measurement of a unstable atom decay, which emits a gamma ray as a trigger of the cat execution.
The problem of the gravitational collapse of small mass in the higher derivative and ghost free theories of gravity is discussed. It will be demonstrated how higher derivative and non-local modifications of gravity equations regularizes static and dynamical solutions. Boosting a static solution of the linearized equations for the gravitational potential of a point mass we obtain a solution for the field of the ultra-relativistic source (gyraton). Using the latter we construct solutions for the collapsing spherical (thin and thick) null shell.
In 1981 Bill discovered an analogy between the propagation of fields in the vicinity of
astrophysical black holes and the that of small excitations in fluids. He postulated that this
analogy allows one to test, challenge and verify, in tabletop experiments, the elusive
processes of black hole mass and angular momentum loss. Indeed, 34 years later
analogue gravity experiments are carried out all over the world to implement his idea.
The last decade has seen the impressive development of quantum information science, both in theory and in experiment. There are many measures that can be used to assess the achievements in the field: new algorithms, new applications and larger quantum processors, to name a few. The discovery of quantum algorithms has demonstrated the potential power of quantum information.
As pointed out by Bill some years ago, to realize this potential requires the ability to overcome the imprecision and imperfection inherent in physical systems.