We have searched for large deviations from Newtonian gravity by means of a finite-frequency microcantilever-based experiment. Our data eliminate from consideration mechanisms of deviation that posit strengths approximately 10(4) times Newtonian gravity at length scales of 20 microm. This measurement is 3 orders of magnitude more sensitive than others that provide constraints at similar length scales.

Several recent theories suggest that light moduli or particles in "large" extra dimensions could mediate macroscopic forces exceeding gravitational strength at length scales below a millimeter. Such new forces can be parameterized as a Yukawa-type correction to the Newtonian potential of strength α relative to gravity and range λ. To extend the search for such new physics we have improved our apparatus utilizing cryogenic micro-cantilevers capable of measuring attonewton forces, which now includes a switchable magnetic force for calibration. Our most recent experimental constraints on Yukawa-type deviations from Newtonian gravity are more than three times as stringent as our previously published results, and represent the best bound in the range of 5 − 15 µm, with a 95% confidence exclusion of forces with |α| > 14,000 at λ = 10 µm.

We develop a new comagnetometer using 21 Ne atoms with nuclear spin I = 3/2 and Rb atoms polarized by spin-exchange with K atoms to search for tensor interactions that violate local Lorentz invariance. We frequently reverse orientation of the experiment and search for signals at the first and second harmonics of the sidereal frequency. We constrain 4 of the 5 spatial Lorentz-violating coefficients c n jk that parameterize anisotropy of the maximum attainable velocity of a neutron at a level of 10 −29 , improving previous limits by 2 to 4 orders of magnitude and placing the most stringent constrain on deviations from local Lorentz invariance.PACS numbers: 11.30. Cp, 21.30.Cb, 32.30.Dx The Michelson-Morley experiment and its successors have established that the speed of light is isotropic to a part in 10 17 [1,2]. Similarly, possible anisotropy in the maximum attainable velocity (MAV) for a massive particle [3] has been constrained by Hughes and Drever NMR experiments [4,5] and their successors to a part in 10 27[6]. These experiments form the basis for the principle of local Lorentz invariance (LLI). Together with the weak equivalence principle and the position invariance principle, they constitute the Einstein equivalence principle that is the basis of general relativity [7]. Measurements of tensor NMR energy shifts [8,9] are particularly sensitive to variation in MAV due to a finite kinetic energy of valence nucleons. They place the most stringent limits on violation of LLI within the T H µ formalism [10] describing deviations from the Einstein Equivalence Principle as well as within more general Standard Model Extension (SME) [11]. They compare favorably even to the limits on variation in MAV from ultra-high energy cosmic rays and other astrophysical phenomena [12][13][14]. It can be argued that Lorentz invariance is likely to be broken at some level by the effects of quantum gravity, which contains a dimensionfull Planck scale that is not Lorentzinvariant. Popular ideas for quantum gravity theories, such as recently proposed Hořava-Lifshitz model [15], explicitly violate Lorentz symmetry. CPT-even tensor Lorentz-violating effects, such as variation in MAV, are particularly interesting to explore because they can arise from purely kinematic violation of Lorentz invariance, do not require explicit particle spin coupling at the fundamental level, and do not suffer from fine-tuning problems associated with CPT-odd Lorentz-violating vector spin interactions [16,17].Here we describe a new comagnetometer that is sensitive to anisotropy in neutron MAV at 10 −29 level. The idea of the experiment is based on the K-3 He comagnetometer, previously used to constrain Lorentz-violating vector spin interactions [18]. The 3 He (I = 1/2) is replaced by 21 Ne (I = 3/2) to allow measurements of tensor anisotropy. In addition, since the gyromagnetic ratio of 21 Ne is about an order of magnitude smaller than that of 3 He, the comagnetometer has an order of magnitude better energy resolution for the same level of magnetic field ...

We performed a search for neutron spin coupling to a Lorentz- and CPT-violating background field using a magnetometer with overlapping ensembles of K and ³He atoms. The comagnetometer is mounted on a rotary platform for frequent reversal of its orientation. We measure sidereal oscillations in the signal to search for anomalous spin coupling of extra-solar origin. We determine the equatorial components of the background field interacting with the neutron spin to be b˜Xn=(0.1 ± 1.6) × 10⁻³³ GeV and b˜Yn=(2.5 ± 1.6) × 10⁻³³ GeV, improving on the previous limit by a factor of 30. This measurement represents the highest energy resolution of any spin anisotropy experiment.

Solutions to many of the world's problems depend upon materials research and development. However, advanced materials can take decades to discover and decades more to fully deploy. Humans and robots have begun to partner to advance science and technology orders of magnitude faster than humans do today through the development and exploitation of closed-loop, autonomous experimentation systems. This review discusses the specific challenges and opportunities related to materials discovery and development that will emerge from this new paradigm. Our perspective incorporates input from stakeholders in academia, industry, government laboratories, and funding agencies. We outline the current status, barriers, and needed investments, culminating with a vision for the path forward. We intend the article to spark interest in this emerging research area and to motivate potential practitioners by illustrating early successes. We also aspire to encourage a creative reimagining of the next generation of materials science infrastructure. To this end, we frame future investments in materials science and technology, hardware and software infrastructure, artificial intelligence and autonomy methods, and critical workforce development for autonomous research.