Article

# Torsion-balance tests of the weak equivalence principle

(Impact Factor: 3.17). 07/2012; 29(18). DOI: 10.1088/0264-9381/29/18/184002
Source: arXiv

ABSTRACT

We briefly summarize motivations for testing the weak equivalence principle
and then review recent torsion-balance results that compare the differential
accelerations of beryllium-aluminum and beryllium-titanium test body pairs with
precisions at the part in $10^{13}$ level. We discuss some implications of
these results for the gravitational properties of antimatter and dark matter,
and speculate about the prospects for further improvements in experimental
sensitivity.

### Full-text

Available from: Stephan Schlamminger, Mar 19, 2014
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• "We also list here the available direct constraints on the dimensionless Eötvös parameter, quantifying violations to the Weak Equivalence Principle. These stem from torsion balance – 6 – tests, leading to [35] η = (−0.7 ± 1.3) × 10 −13 , (3.4) while from lunar laser ranging one finds [36] "
##### Article: Dark energy and Equivalence Principle constraints from astrophysical tests of the stability of the fine-structure constant
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ABSTRACT: Astrophysical tests of the stability of fundamental couplings, such as the fine-structure constant $\alpha$, are becoming an increasingly powerful probe of new physics. Here we discuss how these measurements, combined with local atomic clock tests and Type Ia supernova and Hubble parameter data, constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, $\zeta$, to the electromagnetic sector) the $\alpha$ variation. Specifically, current data tightly constrains a combination of $\zeta$ and the present dark energy equation of state $w_0$. Moreover, in these models the new degree of freedom inevitably couples to nucleons (through the $\alpha$ dependence of their masses) and leads to violations of the Weak Equivalence Principle. We obtain indirect bounds on the E\"otv\"os parameter $\eta$ that are typically stronger than the current direct ones. We discuss the model-dependence of our results and briefly comment on how the forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.
Journal of Cosmology and Astroparticle Physics 08/2015; 2015(08). DOI:10.1088/1475-7516/2015/08/047 · 5.81 Impact Factor
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• "In Newtonian language, the difference between inertial mass (the mass appearing in Newton's second law) and gravitational mass (the mass appearing in Newton's law of gravity) must be exactly zero for the WEP to be respected. For ordinary baryonic matter, modern experiments using torsion balances report that the difference between inertial and gravitational masses is zero at the 10 −13 level [11]. Thus, violations of the WEP in the visible sector are tightly constrained. "
##### Article: Cosmological Constraints on the Gravitational Interactions of Matter and Dark Matter
[Hide abstract]
ABSTRACT: Although there is overwhelming evidence of dark matter from its gravitational interaction, we still do not know its precise gravitational interaction strength or whether it obeys the equivalence principle. Using the latest available cosmological data and working within the framework of $\Lambda\mbox{CDM}$, we first update the measurement of the Newton's constant for all matter: $G_N=7.26^{+0.27}_{-0.27}\times 10^{-11}\,\mbox{m}^{3}\mbox{kg}^{-1}\mbox{s}^{-2}$, which differs by $2.2 \sigma$ from the standard laboratory-based value. In general relativity, dark matter equivalence principle breaking can be mimicked by a long-range dark matter force mediated by an ultra light scalar field. Using the Planck three year data, we find that the dark matter "fifth-force" strength is constrained to be weaker than $10^{-4}$ of the gravitational force. We also introduce a phenomenological, post-Newtonian two-fluid description to explicitly break the equivalence principle by introducing a difference between dark matter inertial and gravitational masses. Depending on the decoupling time of the dark matter and ordinary matter fluids, the ratio of the dark matter gravitational mass to inertial mass is constrained to be unity at the $10^{-6}$ level.
Journal of Cosmology and Astroparticle Physics 05/2015; 2015(10). DOI:10.1088/1475-7516/2015/10/029 · 5.81 Impact Factor
• "where the sum runs over all SM massive vector bosons V , M V is the standard mass of the boson and V ν are the components of the wavefunction of the corresponding massive vector boson. Λ X is a very large energy scale, which is strongly constrained by equivalence principle tests, including lunar laser ranging [27] [28] and the EötWash experiment [29] [30] (see also [31] for constraints "
##### Article: Constraining scalar dark matter with Big Bang nucleosynthesis and atomic spectroscopy
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ABSTRACT: We demonstrate that massive fields, such as dark matter, can directly produce a cosmological evolution of the fundamental constants of Nature. We show that a scalar or pseudoscalar (axion-like) dark matter field $\phi$, which forms a coherently oscillating classical field and interacts with Standard Model particles via quadratic couplings in $\phi$, produces `slow' cosmological evolution and oscillating variations of the fundamental constants. We derive limits on the quadratic interactions of $\phi$ with the photon, electron and light quarks from measurements of the primordial $^4$He abundance produced during Big Bang nucleosynthesis and recent atomic dysprosium spectroscopy measurements. These limits improve on existing constraints by up to 15 orders of magnitude. We also derive limits on the previously unconstrained linear and quadratic interactions of $\phi$ with the massive vector bosons from measurements of the primordial $^4$He abundance. Reference: Y. V. Stadnik, V. V. Flambaum, Physical Review Letters 115, 201301 (2015).