Massive phonons and gravitational dynamics in a photon-fluid model

Abstract

We theoretically investigate the excitation dynamics in a photon-fluid with both local and nonlocal interactions. We show that the interplay between locality and an infinite-range nonlocality gives rise to a gapped Bogoliubov spectrum of elementary excitations which, at lower momenta, correspond to massive particles (phonons) with a relativistic energy-momentum relation. In this regime and in the presence of an inhomogeneous flow the density fluctuations are governed by the massive Klein-Gordon equation on the acoustic metric and thus propagate as massive scalar fields on a curved spacetime. We finally demonstrate that in the non-relativistic limit the phonon modes behave as self-gravitating quantum particles with an effective Schrödinger-Newton dynamics, although with a finite-range gravitational interaction and a non-zero cosmological constant. Our photon-fluid represents a viable alternative to BEC models for "emergent-gravity" scenarios and offers a promising setting for analogue simulations of quantum gravity phenomenology and semiclassical gravity.

Acoustic black-hole bombs and scalar clouds in a photon-fluid model

“…The formal equivalence between phonons propagating on top of an inhomogeneous photon-fluid and the evolution of scalar fields in curved spacetime can be established starting from the Bogoliubov-de Gennes equations ( 7)-( 8) in the limit K ≪ K c [41]. To this end, we apply the operator (∂…”

“…Interestingly, photon-fluids with both local and nonlocal optical nonlinearities support massive elementary excitations which, at lower momenta, correspond to massive phonons with a relativistic energy-momentum relation [41]. In this system, we investigate the phonon dynamics over a draining vortex flow, as the acoustic analogue of a massive scalar field on a rotating BH.…”

Stationary scalar clouds supported by rapidly-rotating acoustic black holes in a photon-fluid model

“…Interestingly, the potential ( 16) of the composed acoustic-black-hole-stationary-scalar-clouds configurations has an effective binding well in the vicinity of the acoustic horizon. As shown in [23,24,27], in the eikonal largefrequency regime (13), one can express the WKB resonance condition for the bound-state field configurations of the one-dimensional Schrödinger-like ordinary differential equation ( 14) in the remarkably compact form…”

“…Photon-fluids are nonlinear optical systems whose physical and mathematical properties can be described by the hydrodynamic equations of an interacting Bose gas [9][10][11][12]. In particular, it has been shown [9,13] that photon-fluid systems are characterized by the presence of long-wavelength elementary excitations (phonons) that behave as massive scalar fields in an effective acoustic curved spacetime.…”

Coherent soliton states hidden in phase-space and stabilized by gravitational incoherent structures

“…There is a surge of interest in studying analogue gravity phenomena in optical laboratory-based experiments that recreate some aspects of the full gravitational system [32][33][34][35][36][37]. Gravity being inherently nonlinear and nonlocal, the hidden coherent soliton states predicted here could be observed in highly nonlocal nonlinear optics experiments [38][39][40][41][42][43][44][45][46][47], or alternatively in dipolar Bose-Einstein condensates [48].…”