Speaker: Surjeet Rajendran
Title: A Causal Framework for Non-Linear Quantum Mechanics
Room: 3024
Zoom: https://zoom.us/j/186024391
Host: Nemanja
Abstract:
We add non-linear and state-dependent terms to quantum field theory. We show that the resulting low-energy theory, non-linear quantum mechanics, is causal, preserves probability and permits a consistent description of the process of measurement. We explore the consequences of such terms and show that non-linear quantum effects can be observed in macroscopic systems even in the presence of de-coherence. We find that current experimental bounds on these non-linearities are weak and propose several experimental methods to significantly probe these effects. We also expose a fundamental vulnerability of any non-linear modification of quantum mechanics - these modifications are highly sensitive to cosmic history and their locally exploitable effects can dynamically disappear if the observed universe has a tiny overlap with the overall quantum state of the universe, as is predicted in conventional inflationary cosmology. We identify observables that persist in this case and discuss opportunities to detect them in cosmic ray experiments, tests of strong field general relativity and current probes of the equation of state of the universe. Non-linear quantum mechanics also enables novel gravitational phenomena and may open new directions to solve the black hole information problem and uncover the theory underlying quantum field theory and gravitation.
Description:
Valentine's Day
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Description:
Speaker: Alberto Nicolis
Title: An Analog of the Cosmological Constant Problem: Vacuum Energy in Framids
Room: 3024
Zoom: https://zoom.us/j/186024391
Host: Markus Luty
Abstract: The near vanishing of the cosmological constant is one of the most puzzling open problems in theoretical physics. I will consider a system, the so-called framid, that features a technically similar problem. Its stress-energy tensor has a Lorentz-invariant expectation value on the ground state, yet there are no standard, symmetry-based selection rules enforcing this, since the ground state spontaneously breaks boosts. I will describe how we verified the Lorentz invariance of the expectation value in question with explicit one-loop computations, and how these yield the expected result only thanks to highly nontrivial cancellations, which are quite mysterious from the low-energy effective theory viewpoint.
Groundhog Day