Abstract We use previously obtained experimental results by neutron interferometry to effectively constrain the parameter space of several prominent dark energy models. This investigation encompasses the environment-dependent dilaton field, a compelling contender for dark energy that emerges naturally within the strong coupling limit of string theory, alongside symmetron and chameleon fields. Our study presents substantial improvements over previous constraints of the dilaton and symmetron fields, improving parameter constraints by several orders of magnitude. However, the analysis does not yield any new constraints on the chameleon field. Furthermore, we establish constraints for the projected neutron split interferometer, which has recently concluded a decisive proof-of-principle demonstration. Our symmetron simulations reveal that, depending on the parameter values, there are multiple static solutions with an increasing number of nodes and increasing energy inside a cylindrical vacuum chamber. This agrees with results obtained earlier in the literature for infinitely extended parallel plates. Interestingly, while these multiple solutions can correspond to domain walls forming inside the vacuum chamber, we also find solutions that do not reach their vacuum expectation value inside the vacuum chamber, but display multiple nodes nonetheless.

Austria

Hauke Fischer

Christian Käding

France

Hartmut Lemmel

Stephan Sponar

Mario Pitschmann

Search for Dark Energy with Neutron Interferometry Les Houches Lectures on physics beyond the standard model of cosmology Astrophysical tests of modified gravity Search for environment-dependent dilatons Gravity Resonance Spectroscopy and Einstein-Cartan Gravity Schrödinger equation for a non-relativistic particle in a gravitational field confined by two vibrating mirrors Detecting dark domain walls

In modern cosmology, scalar fields with screening mechanisms are often used as explanations for phenomena like dark energy or dark matter. Amongst a zoo of models, the environment dependent dilaton, screened by the Polyakov–Damour mechanism, is one of the least constrained ones. Using recently developed path integral tools for directly computing reduced density matrices, we study the open quantum dynamics of a probe, modelled by another real scalar field, induced by interactions with an environment comprising fluctuations of a dilaton. As the leading effect, we extract a correction to the probe’s unitary evolution, which can be observed as a frequency shift. Assuming the scalar probe to roughly approximate a cold atom in matter wave interferometry, we show that comparing the predicted frequency shifts in two experimentally distinct setups has the potential to exclude large parts of the dilaton parameter space.

Caroline Voith

Dilaton-induced open quantum dynamics

We demonstrate the power of a first principle-based and practicable method that allows for the perturbative computation of reduced density matrix elements of an open quantum system without making use of any master equations. The approach is based on techniques from nonequilibrium quantum field theory such as thermo field dynamics, the Schwinger-Keldsyh formalism, and the Feynman-Vernon influence functional. It does not require the Markov approximation and is essentially a Lehmann-Szymanzik-Zimmermann-like reduction. To illustrate this method, we consider a real scalar field as an open quantum system interacting with an environment comprising another real scalar field. We give a general formula that allows for the perturbative computation of density matrix elements for any number of particles in a momentum basis. Finally, we consider a simple toy model and use this formula to obtain expressions for some of the system’s reduced density matrix elements.

New method for directly computing reduced density matrices

We consider the environment-dependent dilaton in the laboratory and the solar system and derive approximate analytical solutions to the field theory equations of motion in the presence of a one or two mirror system or a sphere. The solutions obtained herein can be applied to qBOUNCE experiments, neutron interferometry and for the calculation of the dilaton field induced “Casimir force” in the Cannex experiment as well as for Lunar Laser Ranging. They are typical of the Damour–Polyakov screening mechanism whereby deviations from General Relativity are suppressed by a vanishingly small direct coupling of the dilaton to matter in dense environments. We specifically focus on dilaton models which are compatible with the late time acceleration of the expansion of the Universe, i.e. the cosmological dilaton. We show how future laboratory experiments will essentially test a region of parameter space with  $$A_2\simeq \lambda ^2$$  <math> <mrow> <msub> <mi>A</mi> <mn>2</mn> </msub> <mo>≃</mo> <msup> <mi>λ</mi> <mn>2</mn> </msup> </mrow> </math>   where  $$A_2$$  <math> <msub> <mi>A</mi> <mn>2</mn> </msub> </math>   is the quadratic coupling strength of the dilaton to matter and  $$\lambda $$  <math> <mi>λ</mi> </math>   is the steepness of the exponential runaway potential. Current constraints favour the large  $$A_2$$  <math> <msub> <mi>A</mi> <mn>2</mn> </msub> </math>   regime implying that the environment-dependent dilaton satisfies two of the swampland conjectures, i.e. the distance conjecture whereby the field excursion should not exceed the Planck scale and the de Sitter conjecture specifying that the running dilaton potential should be steep enough with a large  $$\lambda $$  <math> <mi>λ</mi> </math>  .

Philippe Brax

The environment dependent dilaton in the laboratory and the solar system

We present a new color decomposition for QCD amplitudes at one-loop level as a generalization of the Del Duca-Dixon-Maltoni and Johansson-Ochirov decomposition at tree level. Starting from a minimal basis of planar primitive amplitudes we write down a color decomposition that is free of linear dependencies among appearing primitive amplitudes or color factors. The conjectured decomposition applies to any number of quark flavors and is independent of the choice of gauge group and matter representation. The results also hold for higher-dimensional or supersymmetric extensions of QCD. We provide expressions for any number of external quark-antiquark pairs and gluons.