non-Newtonian Gravity Research Articles

Gravitational interaction of neutrinos in models with large extra dimensions

We discuss the interplay between direct constraints on non-Newtonian gravity and particle-physics bounds in models with large extra dimensions. Existing and future bounds and the most effective ways of further testing these models in gravitational experiments are compared and discussed.

Interaction of rheology, geometry, and process in coating flow

A final coating of uniform thickness implies good leveling and the avoidance of defects during film formation. Though generally desired, this objective is often unmet. The outcome of a coating process depends on the nonlinear interaction of the rheology, process variables, and substrate geometry. Understanding the role of rheology is complicated by difficulties in linking fundamental rheological properties with coating performance. During a coating process, forces of varying type, magnitude and duration act on the fluid film. For non-Newtonian coatings the viscosity varies with both time and position within the coating layer, making predictions of flow behavior quite difficult. One answer is computer simulation, using numerical techniques to solve a set of nonlinear differential equations governing the flow. The rheological and other physical properties are parameter values for the program. We present results of mathematical modeling and numerical simulation of a coating imperfection known as a “dripmark.” The model includes non-Newtonian rheology, substrate shape, surface tension, and gravity. We compare theoretical prediction with experimental observation in a study of two architectural paints. We also describe a new method of quantitatively measuring the surface profile of a coating defect.

Transient coating flow of a thin non-Newtonian fluid film

The interplay between non-Newtonian effects, gravity, and substrate topography is examined in this theoretical study for the transient two-dimensional flow of a thin non-Newtonian film. The study is a continuation of the previous work by Khayat and Welke [Phys. Fluids 13, 355 (2001)], which focused on the influence of inertia on a Newtonian film. The fluid emerges from a channel and is driven by a pressure gradient maintained inside the channel. The substrate is assumed to be stationary and of arbitrary shape. The flow is dictated by the thin-film equations of the “boundary layer” type, which are solved by expanding the flow field in terms of orthonormal modes in the transverse direction and using the Galerkin projection, combined with a time-stepping implicit scheme, and integration along the flow direction. Gravity and substrate topography can have a significant effect on transient behavior, but this effect varies significantly, depending on whether the fluid is Newtonian, shear thinning or shear thickening. Wave formation and propagation, as well as steady film flow are examined. It is found that shear-thickening fluids tend to accumulate near the channel exit, exhibiting a standing wave that grows with time. This behavior clearly illustrates the difficulty faced with coating shear-thickening fluids at any level of inertia. The influence of the substrate topography has been explored in the case of undulated substrate.

EXPERIMENTAL HINTS OF GRAVITY IN LARGE EXTRA DIMENSIONS?

Recent conjectures suggest the universe may have large extra dimensions, through which gravity propagates. This implies gross departures from Newton's law of gravity at small length scales. Here I consider some implications for particle dynamics on scales comparable to the compactification radius, R c ≲1 mm. During planet formation, coalescence of micron sized dust grains to planetesimals is a rate critical step. Blum et al. (2000) found dust grain aggregates form low fractal dimension structures in microgravity, consistent with high angular momentum coalescence. I consider the effects of non-Newtonian gravity on dust aggregation on scales less than R c and show they naturally coalesce into low-dimensional structures with high specific angular momentum. We infer R c ≈80 microns.

Non-Newtonian gravity and coherence properties of light

In this work the possibility of detecting a non-Newtonian contribution to the gravitational potential by means of its effects upon the first and second-order coherence properties of light is analyzed. It will be proved that, in principle, the effects of a fifth force upon the correlation functions of electromagnetic radiation could be used to detect the existence of new forces. Some constraints upon the experimental parameters will also be deduced.

Constraints on non-Newtonian gravity from the Casimir force measurements between two crossed cylinders

Constraints on the Yukawa-type corrections to Newtonian gravitational law are obtained resulting from the measurement of the Casimir force between two crossed cylinders. The new constraints are stronger than those previously derived in the interaction range between 1.5 nm and 11 nm. The maximal strengthening in 300 times is achieved at 4.26 nm. Possible applications of the obtained results to the elementary particle physics are discussed.

Quintessence, scalar-tensor theories, and non-Newtonian gravity

We discuss some of the issues which we encounter when we try to invoke the scalar-tensor theories of gravitation as a theoretical basis of quintessence. One of the advantages of appealing to these theories is that they allow us to implement the scenario of a ``decaying cosmological constant,'' which offers a reasonable understanding of why the observed upper bound of the cosmological constant is smaller than the theoretically natural value by as much as 120 orders of magnitude. In this context, the scalar field can be a candidate of quintessence in a broader sense. We find, however, a serious drawback in the prototype Brans-Dicke model with $\Lambda$ added; a static universe in the physical conformal frame which is chosen to have constant particle masses. We propose a remedy by modifying the matter coupling of the scalar field taking advantage of scale invariance and its breakdown through quantum anomaly. By combining this with a conjecture on another cosmological constant problem coming from the vacuum energy of matter fields, we expect a possible link between quintessence and non-Newtonian gravity featuring violation of Weak Equivalence Principle and intermediate force range, likely within the experimental constraints. A new prediction is also offered on the time-variability of the gravitational constant.

New constraints for non-Newtonian gravity in the nanometer range from the improved precision measurement of the Casimir force

We obtain constraints on non-Newtonian gravity following from the improved precision measurement of the Casimir force by means of an atomic force microscope. The hypothetical force is calculated in an experimental configuration (a sphere above a disk both covered by two metallic layers). The strengthenings of constraints up to 4 times comparing the previous experiment and up to 560 times comparing the Casimir force measurements between dielectrics are obtained in the interaction range $5.9 \mathrm{nm}<~\ensuremath{\lambda}<~115 \mathrm{nm}.$ Recent speculations about the presence of some unexplained attractive force in the considered experiment are shown to be unjustified.

Determination of the gravitational constant with a lake experiment: New constraints for non-Newtonian gravity.

The gravitational constant G has been determined at two effective interaction distances 88 m and 112 m, respectively. The 1/${\mathit{r}}^{2}$ dependence of the Newtonian gravitational force law is tested by comparing these results with the currently accepted laboratory determination of G. A high-precision balance was used to measure the weight difference of two 1-kg stainless steel masses as a function of the variable water level of a pumped-storage lake. Water-level changes up to 44 m produced a maximum weight difference of 1390 \ensuremath{\mu}g, which could be measured with a resolution of 0.5 \ensuremath{\mu}g. The difference measurement was carried out to diminish several systematic effects; e.g., tides and balance drifts become negligible. Basically, the measurement directly yields the gravitational interaction between the test masses and the locally moved mass (water and air). Data of weight difference and water level were recorded over several months of the last three years. They yield values for G of (6.669\ifmmode\pm\else\textpm\fi{}0.005)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{m}}^{3}$ ${\mathrm{kg}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}2}$ at 112 m and (6.678\ifmmode\pm\else\textpm\fi{}0.007)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{m}}^{3}$ ${\mathrm{kg}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}2}$ at 88 m, both in agreement with laboratory determinations. New constraints on the strength and range of a composition-independent fifth force are set.

Dark matter and non-newtonian gravity from general relativity coupled to a fluid of strings

An exact solution of Einstein's field equations for a point mass surrounded by a static, spherically symmetric fluid of strings is presented. The solution is singular at the origin. Near the string cloud limit there is a $1/r$ correction to Newton's force law. It is noted that at large distances and small accelerations, this law coincides with the phenomenological force law invented by Milgrom in order to explain the flat rotation curves of galaxies without introducing dark matter. When interpreted in the context of a cosmological model with a string fluid, the new solution naturally explains why the critical acceleration of Milgrom is of the same order of magnitude as the Hubble parameter.

Dwarf spheroidal galaxies and non-Newtonian gravity

view Abstract Citations (54) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Dwarf Spheroidal Galaxies and Non-Newtonian Gravity Gerhard, Ortwin E. ; Spergel, David N. Abstract We derive a virial theorem and an analog for King's formula in modified Newtonian dynamics (MOND; Milgrom 1983) and use these to estimate the mass-to-light ratios (M/Ls) in MOND of the dwarf spheroidal galaxies in the Local Group. We find that the low-velocity dispersion observed in the Fornax dwarf galaxy implies low values for its M/L in MOND: 0.3-1. In particular the derived value in the core of Fornax (0.3) is much lower than expected for a normal old stellar population. Conversely, the velocity-dispersion measurements in Draco and Ursa Minor appear to still require dark matter in MOND. We show that M/L must vary between the dwarf spheroidals around the Galaxy by a factor of order at least 20, even in MOND. Publication: The Astrophysical Journal Pub Date: September 1992 DOI: 10.1086/171763 Bibcode: 1992ApJ...397...38G Keywords: Dark Matter; Dwarf Galaxies; Elliptical Galaxies; Galactic Clusters; Mass To Light Ratios; Galactic Evolution; Gravitation Theory; Kinematics; Metallicity; Astrophysics; COSMOLOGY: DARK MATTER; GALAXIES: ELLIPTICAL AND LENTICULAR; CD; GALAXIES: KINEMATICS AND DYNAMICS; GRAVITATION full text sources ADS | data products SIMBAD (5) NED (5)

Non-Newtonian Gravity and New Weak Forces: an Index of Measurements and Theory

The precise measurement of weak effects plays a pivotal role in metrology and in the determination of the fundamental constants. Hence, the possibility of new weak forces, and the related question of non-Newtonian behaviour of the gravitational force, have been of special interest to both measurement scientists and those involved in precise tests of physical laws. To date there is no compelling evidence for any deviations from the predictions of Newtonian gravity in the nonrelativistic weak-field regime. A significant literature on this question has developed over the past few years, and a host of experiments and theoretical scenarios have been discussed. Moreover, a very close relationship exists between the experimental methodologies used to determine the absolute value of the Newtonian gravitational constant G, and those employed in searches for new weak forces and for breakdowns in the inverse-square law of gravity. We have therefore prepared a new index of measurements of such effects, using the original bibliographic work of Gillies as a starting point, but also including citations to the appropriate theoretical papers in the field. The focus of the present version of the index is then studies of the "fifth force", measurements of gravitational effects on antimatter, searches for a spin-component in the gravitational force, and related phenomena.

Detectability of Non-Newtonian Gravity by Gravity Gradiometry

Detectability of Non-Newtonian Gravity by Gravity Gradiometry

The rise and fall of a non-Newtonian gravity experiment

An experiment was conducted in 1987 in search for a possible non-Newtonian component to gravity. The test compared accurately measured gravity values on a 600 m tower with upward continued surface gravity. The results indicated a dominant attractive non-Newtonian force that asymptotically approached -540 µGal at the top of the tower. An exhaustive search of possible error sources led to the discovery that our surface data did not accurately represent some of the local topographic features. The surface survey was supplemented by gravity data to remove some of the biases that were caused by the misrepresentation. In addition, a rigorous terrain correction was applied to the surface data resulting in terrain-corrected Bouguer anomalies. These anomalies were then upward continued using two independent techniques. The terrain effect was added back to the predicted values at altitude. With this procedure almost the entire non-Newtonian effect was explained. Currently we find no conclusive evidence for a non-Newtonian force over the range of several hundred meters.

Recent history of tower and mine searches for non-Newtonian gravity

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Exponential models of non-Newtonian gravity.

We show that in certain classes of theories the spatial variation of the non-Newtonian potential would be dominantly an exponential rather than a Yukawa potential, and we compare the phenomenological interpretation of the existing data in the exponential and Yukawa models. We also show that generalized forms of the exponential potential can arise naturally from simple mass spectra. Although such models cannot reconcile all of the existing data on non-Newtonian gravity, they have novel properties that can be directly studied experimentally.

Tower gravity experiment: No evidence for non-Newtonian gravity

A test of Newton's inverse-square law of gravitation by Eckhardt, Jekeli, Lazarewicz, Romaides, and Sands using gravity measurements on a tall tower yielded evidence for non-Newtonian gravity. We have refined the analysis of that experiment by including detailed topographic information and conclude that, in fact, no such evidence exists. The accuracy of the experiment constrains the Yukawa-potential coupling constant \ensuremath{\alpha} to be less than 0.001.

FLOWFRONT: Simulation of a lava flow

FLOWFRONT is a C program that simulates the advance of a non-Newtonian fluid, such as a lava, over a digital elevation model (DEM). It requires, in addition to the DEM, a corresponding model of topographic slopes and produces a map of flow thicknesses, normally as a raster image for display. Lava flow is a complicated phenomenon and the main simplifying assumption used here is that supply of new lava to the advancing front is implicit. There are no calculations associated with thermomechanical continuity for the whole flow, only the advance of the flow's front is modeled, which requires significantly less computation. The user must set a number of volume, thickness, and slope parameters, and optionally can vary these incrementally to simulate time-dependent behavior. The program is fast enough to run many times for one volcanic region, allowing the user to assess the effects of changing the empirical parameters, source location, and size, etc. The program should be of use to geologists concerned with modeling hazards associated with lava flows and possibly other non-Newtonian gravity flows.

Possible effect of the local terrain on the Australian fifth-force measurement.

We believe that the local topography can account for most of the positive evidence for non-Newtonian gravity recently reported by Stacey and co-workers. We show that the Hilton mine site in Queensland, Australia, is effectively in a valley and speculate on how this feature could have been missed in the original analysis.

Physical Geodesy Considering the Yukawa-type Potential Term in Non-Newtonian Gravity Field

Physical Geodesy Considering the Yukawa-type Potential Term in Non-Newtonian Gravity Field