Quantum model for entropic springs

Abstract

Motivated by understanding the emergence of thermodynamic restoring forces and oscillations, we develop a quantum-mechanical model of a bath of spins coupled to the elasticity of a material. We show our model reproduces the behavior of a variety of entropic springs while enabling investigation of non-equilibrium resonator states in the quantum domain. We find our model emerges naturally in disordered elastic media such as glasses, and is an additional, expected effect in systems with anomalous specific heat and 1/f noise at low temperatures due to two-level systems that fluctuate.

Tabletop experiments for quantum gravity: a user’s manual

“…This should be viewed roughly in analogy with the hydrodynamic limit of fluid mechanics, in which the underlying quantum atoms lead to semiclassical hydrodynamics at sufficiently long length scales. A variety of such models have been proposed; and their predictions for experiments like those we are studying here are unclear, although there are simple models demonstrating that, entropic forces cannot entangle particles [103] and there has been some debate [104,105] about whether or not these models are consistent with experiments involving gravitationally-bound cold neutron states [5]. We view the types of experiments discussed in this paper as a major opportunity to learn more about such emergent models.…”

Tuning a small electron polaron in FePO4 by P-site or O-site doping based on DFT+U and KMC simulation

“…We calculated the energy barrier of FePO 4 adiabatic hopping to be 0.143 eV, which is close to the previous calculations. 15,68 It can also be seen in Fig. 3(c) that the electron is distributed on two adjacent hopping Fe sites in the transition state during the hopping process.…”

“…† For the pristine system, the energy barriers of adiabatic hopping and diabatic hopping are 0.143 eV and 0.210 eV, respectively, which are consistent with previous calculations. 68 The electron transfer coefficient k el is close to 1, so the hopping of the polaron in the pristine system is recognized as an adiabatic process. For the doped systems, most of the k el values are close to 1 with only a few k el values close to 0, indicating that most of the hopping paths are adiabatic.…”

Newton, entanglement, and the graviton

“…It is not at all clear that this is a general property of emergent interactions. Indeed, one can construct models of entropic forces which produce quantum coherent interactions [83]. Moreover, in AdS/CFT, the bulk graviton exists by construction, at least in the traditional sense of AdS/CFT as a string duality [84], since the closed string has a massless spin-2 excitation.…”