NASA Technical Reports Server (NTRS)
Booth, F. W.; Bruce, R. A. (inventors)
1973-01-01
An apparatus for mixing liquids under conditions of zero gravity is disclosed. The apparatus is comprised of a closed reservoir for the liquids, with a means for maintaining a positive pressure on the liquids in the reservoir. A valved liquid supply line is connected to the reservoir for supplying the reservoir with the liquids to be mixed in the reservoir. The portion of the reservoir containing the liquids to be mixed is in communication with a pump which alternately causes a portion of the liquids to flow out of the pump and into the reservoir to mix the liquids. The fluids in the reservoir are in communication through a conduit with the pump which alternately causes a portion of the fluids to flow out of the pump and into the sphere. The conduit connecting the pump and sphere may contain a nozzle or other jet-forming structure such as a venturi for further mixing the fluids.
NASA Technical Reports Server (NTRS)
Badler, N. I.; Fishwick, P.; Taft, N.; Agrawala, M.
1985-01-01
The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms.
Zero-gravity venting of three refrigerants
NASA Technical Reports Server (NTRS)
Labus, T. L.; Aydelott, J. C.; Amling, G. E.
1974-01-01
An experimental investigation of venting cylindrical containers partially filled with initially saturated liquids under zero-gravity conditions was conducted in the NASA Lewis Research Center 5-second zero-gravity facility. The effect of interfacial mass transfer on the ullage pressure response during venting was analytically determined, based on a conduction analysis applied to an infinitely planer (flat) liquid-vapor interface. This pressure response was compared with both the experimental results and an adiabatic decompression computation.
Zero-gravity quantity gaging system
NASA Technical Reports Server (NTRS)
1989-01-01
The Zero-Gravity Quantity Gaging System program is a technology development effort funded by NASA-LeRC and contracted by NASA-JSC to develop and evaluate zero-gravity quantity gaging system concepts suitable for application to large, on-orbit cryogenic oxygen and hydrogen tankage. The contract effective date was 28 May 1985. During performance of the program, 18 potential quantity gaging approaches were investigated for their merit and suitability for gaging two-phase cryogenic oxygen and hydrogen in zero-gravity conditions. These approaches were subjected to a comprehensive trade study and selection process, which found that the RF modal quantity gaging approach was the most suitable for both liquid oxygen and liquid hydrogen applications. This selection was made with NASA-JSC concurrence.
Induced gravity and Planck zeros
Khuri, N.N.
1982-11-15
Starting with an asymptotically free gauge theory with dynamical symmetry breaking and a mass hierarchy, we investigate the Adler-Zee formula for the induced gravitational constant. We study the two-point function psi(q/sup 2/), constructed with the trace of the energy-momentum tensor. First, we show that if the zeros of psi are at a mass scale significantly below the leading scale, then G/sub ind/ /sup -1/ = 0 (m/sub zero/ /sup 2/) making it impossible to get a realistic G/sub ind/ from the Adler-Zee formula with low-mass zeros. Next we use the Jensen formula to derive a sum rule for Vertical Barm/sub zero/Vertical Bar. The analysis of this sum rule coupled with the result above leads to a dilemma with only one reasonable resolution. To get a realistic G/sub ind/ from the Adler-Zee formula, psi(q/sup 2/) must have a pair of complex-conjugate zeros at q/sup 2/ = M/sub 0/ /sup 2/ +- 2i..gamma..M/sub 0/, where M/sub 0/ is large and of the maximal scale and ..gamma../M/sub 0/<<1. The presence of this zero essentially determines G/sub ind/ /sup -1/. It gives a lower bound, which with our previously derived general upper bound gives (..pi../sup 2//4(ln10)288) C/sub psi/M/sub 0/ /sup 2/< or =(16..pi..G)/sup -1/ < or = (5..pi../sup 2//288) C/sub psi/M/sub 0/ /sup 2/, where C/sub psi/ is the anomaly coefficient, a number easily determined by low-order perturbation theory for any group.
Marangoni bubble motion in zero gravity. [Lewis zero gravity drop tower
NASA Technical Reports Server (NTRS)
Thompson, R. L.; Dewitt, K. J.
1979-01-01
It was shown experimentally that the Marangoni phenomenon is a primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low gravity environment. A mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented. Parameter perturbation theory is used to solve this boundary value problem; the expansion parameter is the Marangoni number. The zeroth, first, and second order approximations for the velocity, temperature and pressure distributions in the liquid and in the bubble, and the deformation and terminal velocity of the bubble are determined. Experimental zero gravity data for a nitrogen bubble in ethylene glycol, ethanol, and silicone oil subjected to a linear temperature gradient were obtained using the NASA Lewis zero gravity drop tower. Comparison of the zeroth order analytical results for the bubble terminal velocity showed good agreement with the experimental measurements. The first and second order solutions for the bubble deformation and bubble terminal velocity are valid for liquids having Prandtl numbers on the order of one, but there is a lack of appropriate data to test the theory fully.
Experiments with the Skylab fire detectors in zero gravity
NASA Technical Reports Server (NTRS)
Linford, R. M. F.
1972-01-01
The Skylab fire detector was evaluated in a zero gravity environment. To conduct the test, small samples of spacecraft materials were ignited in a 5 psi oxygen-rich atmosphere inside a combustion chamber. The chamber free-floated in the cabin of a C-135 aircraft, as the aircraft executed a Keplerian parabola. Up to 10 seconds of zero-gravity combustion were achieved. The Skylab fire-detector tubes viewed the flames from a simulated distance of 3m, and color movies were taken to record the nature of the fire. The experiments established the unique form of zero-gravity fires for a wide range of materials. From the tube-output data, the alarm threshold and detector time constant were verified for the Skylab Fire Detection System.
Combustion of solid carbon rods in zero and normal gravity
NASA Technical Reports Server (NTRS)
Spuckler, C. M.; Kohl, F. J.; Miller, R. A.; Stearns, C. A.; Dewitt, K. J.
1979-01-01
In order to investigate the mechanism of carbon combustion, spectroscopic carbon rods were resistance ignited and burned in an oxygen environment in normal and zero gravity. Direct mass spectrometric sampling was used in the normal gravity tests to obtain concentration profiles of CO2, CO, and O2 as a function of distance from the carbon surface. The experimental concentrations were compared to those predicted by a stagnant film model. Zero gravity droptower tests were conducted in order to assess the effect of convection on the normal gravity combustion process. The ratio of flame diameter to rod diameter as a function of time for oxygen pressures of 5, 10, 15, and 20 psia was obtained for three different diameter rods. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter.
Liquid motions in containers in zero-gravity
J. P. B. Vreeburg
1977-01-01
Projected Spacelab experiments on sloshing and oscillations of liquid confined within an enclosure under zero-gravity conditions are discussed. Slight deviations from zero-g termed g-jitter are anticipated as a result of crew movements in the spacecraft, attitude corrections, and unforeseen phenomena. This g-jitter might affect such sensitive transport phenomena as crystal growth. Simulated experiments on earth (using neutral buoyancy tanks, drop
Zero gravity simulation technique of five freedom docking test bed
Zhang Chongjun; Lai Yinan; Zhang Guangyu
2004-01-01
The paper aimed to solve the weightless problem of the active docking ring (ADR) of a docking mechanism. The paper proposes a lift-on zero gravity simulation method with compact structure, which has an internal support rope for the active docking ring in the space docking process. The internal support structure ensures that the ADR rotates freely in three-axis direction. The
Acceleration display system for aircraft zero-gravity research
NASA Technical Reports Server (NTRS)
Millis, Marc G.
1987-01-01
The features, design, calibration, and testing of Lewis Research Center's acceleration display system for aircraft zero-gravity research are described. Specific circuit schematics and system specifications are included as well as representative data traces from flown trajectories. Other observations learned from developing and using this system are mentioned where appropriate. The system, now a permanent part of the Lewis Learjet zero-gravity program, provides legible, concise, and necessary guidance information enabling pilots to routinely fly accurate zero-gravity trajectories. Regular use of this system resulted in improvements of the Learjet zero-gravity flight techniques, including a technique to minimize later accelerations. Lewis Gates Learjet trajectory data show that accelerations can be reliably sustained within 0.01 g for 5 consecutive seconds, within 0.02 g for 7 consecutive seconds, and within 0.04 g for up to 20 second. Lewis followed the past practices of acceleration measurement, yet focussed on the acceleration displays. Refinements based on flight experience included evolving the ranges, resolutions, and frequency responses to fit the pilot and the Learjet responses.
The response of single human cells to zero-gravity
NASA Technical Reports Server (NTRS)
Montgomery, P. O., Jr.; Cook, J. E.; Reynolds, R. C.; Paul, J. S.; Hayflick, L.; Stock, D.; Shulz, W. W.; Kimzey, S. L.; Thirolf, R. G.; Rogers, T.
1977-01-01
Microscopic and histochemical evaluations of human embrionic lung cells after exposure to zero-gravity are reported. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of fixed cells revealed no effects on the cultures. Minor unexplained differences have been found in biochemical constituents of the samples.
Zero Gravity Facility for space vehicle fluid systems research.
NASA Technical Reports Server (NTRS)
Petrash, D. A.; Corpas, E. L.
1973-01-01
Review of the major features and characteristics of the 5- to 10-second Zero Gravity Facility of the NASA Lewis Research Center. The facility consists primarily of a vertical (155 m) vacuum chamber wherein a variety of free-fall (weightless) experiments can be performed.-
Zero Gravity Cryogenic Vent System Concepts for Upper Stages
Alain Ravex; Robin Flachbart; Barney Holt
1999-01-01
The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid\\/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical
Experiments on thermoacoustic convection heat transfer in gravity and zero-gravity environments
NASA Technical Reports Server (NTRS)
Parang, Masood; Salah-Eddine, Adel
1987-01-01
The results of an experimental study of thermoacoustic convection (TAC) heat transfer in gravity and zero-gravity environments are presented. The experimental apparatus consisted of a cylinder containing air as the compressible fluid. The enclosed air was heated electrically at the top surface which consisted of a thin high-resistance steel foil connected to a power source. Thermocouples were used to measure the transient temperature of the air on the axis of the cylinder and the heated surface in the both zero-gravity and gravity environments. The zero-gravity tests were performed in the Zero-Gravity Drop Tower Facility of NASA-Lewis Research Center. The experimental results were corrected for the error due to radiation absorption by the thermocouples. A conduction-only numerical heat transfer model was developed to compute the transient air temperature in the cylindrical geometry. The results were compared to the experimental data to determine the significance of the thermoacoustic convection heat transfer mechanism. It is observed that the rate of heat transfer to the air measured during the experiments is consistently higher than that obtained by the conduction-only solution indicating a significant presence of the TAC heat transfer. Further experiments are planned to measure directly (1) the radiative heat transfer contribution to the rise in the air temperature, and (2) the air pressure oscillations within the cylinder that are responsible for the convective heat transfer mode.
The response of single human cells to zero gravity
NASA Technical Reports Server (NTRS)
Montgomery, P. O., Jr.; Cook, J. E.; Reynolds, R. C.; Paul, J. S.; Hayflick, L.; Schulz, W. W.; Stock, D.; Kinzey, S.; Rogers, T.; Campbell, D.
1975-01-01
Twenty separate cultures of Wistar-38 human embryonic lung cells were exposed to a zero-gravity environment on Skylab for periods of time ranging from one to 59 days. Duplicate cultures were run concurrently as ground controls. Ten cultures were fixed on board the satellite during the first 12 days of flight. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of the fixed cells revealed no effects of a zero-gravity environment on the ten cultures. Two cultures were photographed with phase time lapse cinematography during the first 27 days of flight. No differences were found in mitotic index, cell cycle, and migration between the flight and control cells. Eight cultures were returned to earth in an incubated state. Karyotyping and chromosome banding tests show no differences between the flight and control cells.
Fluid management system for a zero gravity cryogenic storage system
NASA Technical Reports Server (NTRS)
Lak, Tibor I. (Inventor)
1995-01-01
The fluid management system comprises a mixing/recirculation system including an external recirculation pump for receiving fluid from a zero gravity storage system and returning an output flow of the fluid to the storage system. An internal axial spray injection system is provided for receiving a portion of the output flow from the recirculation pump. The spray injection system thermally de-stratifies liquid and gaseous cryogenic fluid stored in the storage system.
Crew efficiency on first exposure to zero-gravity
NASA Technical Reports Server (NTRS)
Garriott, O. K.; Doerre, G. L.
1977-01-01
Activation task performance of Skylab crews showed improved efficiency as experience was gained in weightlessness living. During three activation intervals, less than 12 man-hours were lost due to reduced efficiency (including the effects of motion sensitivity) while almost 200 man-hours of productive work were delivered. Work rate improved for tasks in which simulation and training time were extensive and for tasks which allowed zero-gravity operations to be optimized.
Gravity as a zero-point-fluctuation force
H. E. Puthoff
1989-01-01
Sakharov has proposed a suggestive model in which gravity is not a separately existing fundamental force, but rather an induced effect associated with zero-point fluctuations (ZPF's) of the vacuum, in much the same manner as the van der Waals and Casimir forces. In the spirit of this proposal we develop a point-particle--ZPF interaction model that accords with and fulfills this
Development of a compact dilution refrigerator for zero gravity operation
NASA Technical Reports Server (NTRS)
Roach, Pat R.; Helvensteijn, Ben
1990-01-01
A compact dilution refrigerator design based on internal charcoal adsorption is being tested for operation in zero gravity. This refrigerator is self-contained with no external pumps or gas handling system and provides reliable operation since it has no moving parts. All operations are performed with heaters and are completely computer controlled. The refrigerator is capable of providing many hours of operation at very low temperature before the charcoal pumps must be recycled.
Dynamics of fluid interfaces under vibrations in zero gravity conditions
NASA Astrophysics Data System (ADS)
Lyubimova, Tatyana; Beysens, Daniel; Gandikota, Gurunath; Ivantsov, Andrey
In experiments [1] it was found that under sufficiently intensive horizontal vibrations the interface of two immiscible fluids subjected to the gravity field becomes unstable and the formation of frozen wave is observed. The theoretical investigation of this phenomenon was carried out in [2] using high frequency approach. It was shown that the development of frozen waves is related to the Kelvin-Helmholtz instability and analytical formula for neutral curve was obtained. The present work deals with the numerical and experimental investigation of frozen wave formation in zero gravity conditions. Numerical investigation is performed using the volume of fluid method. The calculations show that at the first stage of the process the evolution of interface shape is similar the formation of the frozen wave in normal gravity conditions. The further evolution leads to the formations of the system of striates since in the absence of gravity there is no force that could limit the growth of interface deflection. The dependences of the striates period on the fluid viscosities, vibration amplitude and frequency and cavity height are obtained. The mechanism of the wavelength selection is discussed. Numerical results are compared with the data obtained for two-phase system CO2 in space experiments and for H2 under magnetic compensation of gravity. The work was supported by the Government of Perm Region (Contract number C-26/212). 1. G.H.Wolf. Z. Phys., 227, H 3, 291 (1969). 2. D.V.Lyubimov, A.A.Cherepanov. Fluid Dynamics, 21, 849 (1987).
Investigation of crystal growth from solutions. [in zero gravity environments
NASA Technical Reports Server (NTRS)
Miyagawa, I.
1974-01-01
The quality was investigated of a crystal of Rochelle salt grown from a solution placed in the zero-gravity environment of Skylab 4. The crystal has the following unique features: (1) the typical cavity is a long tube extending along the c-axis, the average length being 4mm, compared to 0.1mm that is the average size for earth-grown crystals; and (2) the crystal consists of several single crystals, the axes of which are parallel to each other. A preliminary measurement was made on the ferroelectric hysteresis curve of this Rochelle salt crystal.
Muscle and the physiology of locomotion. [in zero gravity
NASA Technical Reports Server (NTRS)
Rambaut, P. C.; Nicogossian, A. E.; Pool, S. L.
1983-01-01
NASA's past, current, and planned research on muscle deterioration at zero gravity and development of countermeasures are reviewed; Soviet studies are discussed as well. A definition of muscle mass and strength regulation factors, and improved measurement methods of muscle atrophy are needed. Investigations of tissue growth factors and their receptors, endogenous and exogenous anabolic protein synthesis stimulation, and a potential neurotropic factor are among the projects in progress or planned. At present, vigorous physical exercise during spaceflight is recommended as the most effective countermeasure against skeletal muscle atrophy.
Sediment-transport (wind) experiments in zero-gravity
NASA Astrophysics Data System (ADS)
Iverson, J.; Gillette, D.; Greeley, R.; Lee, J.; MacKinnon, I.; Marshall, J.; Nickling, W.; Werner, B.; White, B.; Williams, S.
1986-05-01
The carousel wind tunnel (CWT) can be a significant tool for the determination of the nature and magnitude of interparticlar forces at threshold of motion. By altering particle and drum surface electrical properties and/or by applying electric potential difference across the inner and outer drums, it should be possible to separate electrostatic effects from other forces of cohesion. Besides particle trajectory and bedform analyses, suggestions for research include particle aggregation in zero and sub-gravity environments, effect of suspension-saltation ratio on soil abrasion, and the effects of shear and shearfree turbulence on particle aggregation as applied to evolution of solar nebula.
Ball Lightning in Zero Gravity in the Laboratory
NASA Astrophysics Data System (ADS)
Alexeff, Igor; Parameswaran, Sriram; Grace, Michael
2004-11-01
We have created balls of orange plasma in atmospheric - pressure air that survive for over 1/2 second without power input. The technique used was to create a pulsed horizontal electric arc in a zero - gravity environment using 6 neon - sign transformers in parallel, each producing 16,000 V at 60 mA. The zero - gravity environment reduces heat losses by reducing thermal convection, creating a larger ball. Previous work (1) suggests that the ball lifetime scales as the square of the ball radius. The balls were photographed after power turnoff with a high - speed 16 mm movie camera. Movies of the balls being formed and decaying will be shown. We suggest that there are several other forms of ball lightning (2). 1.Igor Alexeff et. al. International Conference On Plasma Science, Jeju, Korea, June 2-5, 2003, Conference Record, p 254. 2. Igor Alexeff and Mark Rader, IEEE Transactions on Plasma Science, Vol. 20, No. 6, Dec. 1992, pp.669-671. Igor Alexeff and Mark Rader, Fusion Technology, Vol. 27, May 1995, p. 271.
Ocular Blood Flow Measured Noninvasively in Zero Gravity
NASA Technical Reports Server (NTRS)
Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.
2003-01-01
In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.
Cool flames at terrestrial, partial, and near-zero gravity
Foster, Michael; Pearlman, Howard [Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)
2006-10-15
Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra<600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; and reduced gravity, {approx}10{sup -2}g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350? deg C (593-623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive-diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results. (author)
Combustion of solid carbon rods in zero and normal gravity
NASA Astrophysics Data System (ADS)
Spuckler, C. M.
1981-05-01
In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.
Zero-Gravity Vortex Vent and PVT Gaging System
NASA Technical Reports Server (NTRS)
Downey, M. G.; Trevathan, J. T.
1989-01-01
Space Station and satellite reservicing will require the ability to vent gas on orbit from liquid supply or storage tanks and to gage liquid quantity under microgravity conditions. In zero gravity, (zero-g) the vortex vent is capable of venting gas from a tank of liquid containing gas randomly distributed as bubbles. The concept uses a spinning impeller to create centrifugal force inside a vortex tube within a tank. This creates a gas pocket and forces the liquid through a venturi and back into the tank. Gas is then vented from the gas pocket through a liquid detector and then out through an exhaust port. If the liquid detector senses liquid in the vent line, the fluid is directed to the low-pressure port on the venturi and is returned to the tank. The advantages of this system is that it has no rotating seals and is compatible with most corrosive and cryogenic fluids. A prototype was designed and built at the NASA Johnson Space Center and flown on the KC-135 zero-g aircraft. During these test flights, where microgravity conditions are obtained for up to 30 sec, the prototype demonstrated that less than 0.10 percent of the volume of fluid vented was liquid when the tank was half full of liquid. The pressure volume temperature (PVT) gaging system is used in conjunction with the vortex vent to calculate the amount of liquid remaining in a tank under microgravity conditions. The PVT gaging system is used in conjunction with the vortex vent to gage liquid quantity in zero or low gravity. The system consists of a gas compressor, accumulator, and temperature and pressure instrumentation. To measure the liquid in a tank a small amount of gas is vented from the tank to the compressor and compressed into the accumulator. Pressure and temperature in the tank and accumulator are measured before and after the gas transfer occurs. Knowing the total volume of the tank, the volume of the accumulator, the volume of the intermediate lines, and initial and final pressures and temperatures, the mass of the gas leaving the tank is equated to the mass of the gas entering the accumulator. The volume of liquid remaining in the tank is calculated using the ideal gas law.
Experiments on the properties of superfluid helium in zero gravity
NASA Technical Reports Server (NTRS)
Mason, P.; Collins, D.; Petrac, D.; Yang, L.; Edeskuty, F.; Williamson, K.
1976-01-01
The paper describes a research program designed to study the behavior of superfluid liquid helium in low and zero gravity in order to determine the properties which are critically important to its use as a stored cryogen for cooling scientific instruments aboard spacecraft for periods up to several months. The experiment program consists of a series of flights of an experiment package on a free-fall trajectory both on an aircraft and on a rocket. The objectives are to study thickness of thin films of helium as a function of acceleration, heat transfer in thin films, heat transfer across copper-liquid helium interfaces, fluid dynamics of bulk helium in high and low accelerations and under various conditions of rotations, alternate methods of separation of liquid and vapor phases and of efficient venting of the vapor, and undesirable thermomechanical oscillations in the vent pipes. Preliminary results from aircraft tests are discussed.
Zero Gravity Cryogenic Vent System Concepts for Upper Stages
NASA Technical Reports Server (NTRS)
Flachbart, Robin H.; Holt, James B.; Hastings, Leon J.
1999-01-01
The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray bar system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy is required. a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point. the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating, boil-off losses.
Zero Gravity Cryogenic Vent System Concepts for Upper Stages
NASA Technical Reports Server (NTRS)
Flachbart, Robin H.; Holt, James B.; Hastings, Leon J.
2001-01-01
The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space, and would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray-bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray-bar system consists of a recirculation pump, a parallel flow concentric tube heat exchanger, and a spray-bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses.
Comprehensive solution to the cosmological constant, zero-point energy, and quantum gravity problems
Philip D. Mannheim
2011-01-01
We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single\\u000a comprehensive framework. We show that in quantum theories of gravity in which the zero-point energy density of the gravitational\\u000a field is well-defined, the cosmological constant and zero-point energy problems solve each other by mutual cancellation between\\u000a the cosmological constant and the
Steady State Detached Solidification of Water at Zero Gravity
NASA Technical Reports Server (NTRS)
Wang, Yazhen; Regel, Liya L.; Wilcox, William R.
2003-01-01
Steady-state detached solidification of water was calculated using the Moving Meniscus Model. Similar to the experimental observation of many materials in microgravity, detached solidification of water is predicted to occur in a sealed ampoule at zero gravity under proper conditions. For steady detachment, the freezing rate must exceed a critical value, Henry's constant of the dissolved gas must be below a critical value, the temperature of the top of the water must be below a critical value, the contact angle of water on the ampoule wall must exceed a critical value, and the diffusion coefficient must exceed a critical value. Each critical value depends on the physical properties and the other operating conditions. Thus different results are obtained for InSb and water. The critical gas pressure above the melt for water is much smaller than for InSb, the critical freezing rate is larger for water, and the critical contact angle of the melt on the ampoule wall is larger for water. For the gases examined here, the solubilities of Ar, N2 and Ne in water are sufficient for detachment to occur, while the solubility of He is not.
Steady State Detached Solidification of Water at Zero Gravity
NASA Technical Reports Server (NTRS)
Wang, Yazhen; Regel, Liya L.; Wilcox, William R.
2001-01-01
Steady-state detached solidification of water was calculated using the Moving Meniscus Model. Similar to the experimental observation of many materials in microgravity, detached solidification of water is predicted to occur in a sealed ampoule at zero gravity under proper conditions. For steady detachment, the freezing rate must exceed a critical value, Henry's constant of the dissolved gas must be below a critical value, the temperature of the top of the water must be below a critical value, the contact angle of water on the ampoule wall must exceed a critical value, and the diffusion coefficient must exceed a critical value. Each critical value depends on the physical properties and the other operating conditions. Thus different results are obtained for InSb and water. The critical gas pressure above the melt for water is much smaller than for InSb, the critical freezing rate is larger for water, and the critical contact angle of the melt on the ampoule wall is larger for water. For the gases examined here, the solubilities of Ar, N2 and Ne in water are sufficient for detachment to occur, while the solubility of He is not.
Adiabatic demagnetization refrigerator for use in zero gravity
NASA Technical Reports Server (NTRS)
Dingus, Michael L.
1988-01-01
In this effort, a new design concept for an adiabatic demagnetization refrigerator (ADR) that is capable of operation in zero gravity has been developed. The design uses a vortex precooler to lower the initial temperature of magnetic salt from the initial space superfluid helium dewar of 1.8 K to 1.1 K. This reduces the required maximum magnetic field from 4 Tesla to 2 Tesla. The laboratory prototype vortex precooler reached a minimum temperature of 0.78 K, and had a cooling power of 1 mW at 1.1 K. A study was conducted to determine the dependence of vortex cooler performance on system element configuration. A superfluid filled capillary heat switch was used in the design. The laboratory prototype ADR reached a minimum temperature of 0.107 K, and maintained temperatures below 0.125 K for 90 minutes. Demagnetization was carried out from a maximum field of 2 T. A soft iron shield was developed that reduced the radial central field to 1 gauss at 0.25 meters.
Modeling of zero gravity venting: Studies of two-phase heat transfer under reduced gravity
NASA Technical Reports Server (NTRS)
Merte, H., Jr.
1986-01-01
The objective is to predict the pressure response of a saturated liquid-vapor system when undergoing a venting or depressurization process in zero gravity at low vent rates. An experimental investigation of the venting of cylindrical containers partially filled with initially saturated liquids was previously conducted under zero-gravity conditions and compared with an analytical model which incorporated the effect of interfacial mass transfer on the ullage pressure response during venting. A new model is presented to improve the estimation of the interfacial mass transfer. Duhammel's superposition integral is incorporated to approximate the transient temperature response of the interface, treating the liquid as a semi-infinite solid with conduction heat transfer. Account is also taken of the condensation taking place within the bulk of a saturated vapor as isentropic expansion takes place. Computational results are presented for the venting of R-11 from a given vessel and initial state for five different venting rates over a period of three seconds, and compared to prior NASA experiments. An improvement in the prediction of the final pressure takes place, but is still considerably below the measurements.
Zero Gravity Cryogenic Vent System Concepts for Upper Stages
NASA Astrophysics Data System (ADS)
Ravex, Alain; Flachbart, Robin; Holt, Barney
The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray bar system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses. TVS performance testing demonstrated that the spray bar was effective in providing tank pressure control within a 6.89 kPa (1psi) band for fill levels of 90%, 50%, and 25%. Complete destratification of the liquid and ullage was achieved at these fill levels. The axial jet was effective in providing tank pressure control within the same pressure control band at the 90% fill level. However, at the 50% level, the system reached a point at which it was unable to extract enough energy to keep up with the heat leak into the tank. Due to a hardware problem, the recirculation pump operated well below the axial jet design flow rate. Therefore, it is likely that the performance of the axial jet would have improved had the pump operated at the proper flow rate. A CFD model is being used to determine if the desired axial jet performance would be achieved if a higher pump flow rate were available. Testing conducted thus far has demonstrated that both TVS concepts can be effective in destratifying a propellant tank, rejecting stored heat energy, and thus, controlling tank pressure.
Vortex motion phase separator for zero gravity liquid transfer
NASA Technical Reports Server (NTRS)
Howard, Frank S. (inventor); Fraser, Wilson M., Jr. (inventor)
1989-01-01
A vortex motion phase separator is disclosed for transferring a liquid in a zero gravity environment while at the same time separating the liquid from vapors found within either the sender or the receiving tanks. The separator comprises a rigid sender tank having a circular cross-section and rigid receiver tank having a circular cross-section. A plurality of ducts connects the sender tank and the receiver tank. Disposed within the ducts connecting the receiver tank and the sender tank is a pump and a plurality of valves. The pump is powered by an electric motor and is adapted to draw either the liquid or a mixture of the liquid and the vapor from the sender tank. Initially, the mixture drawn from the sender tank is directed through a portion of the ductwork and back into the sender tank at a tangent to the inside surface of the sender tank, thereby creating a swirling vortex of the mixture within the sender tank. As the pumping action increases, the speed of the swirling action within the sender tank increases creating an increase in the centrifugal force operating on the mixture. The effect of the centrifugal force is to cause the heavier liquid to migrate to the inside surface of the sender tank and to separate from the vapor. When this separation reaches a predetermined degree, control means is activated to direct the liquid conveyed by the pump directly into the receiver tank. At the same time, the vapor within the receiver tank is directed from the receiver tank back into the sender tank. This flow continues until substantially all of the liquid is transferred from the sender tank to the receiver tank.
NASA Technical Reports Server (NTRS)
Parang, Masood
1986-01-01
An experimental and analytical study of Thermoacoustic Convection heat transfer in gravity and zero-gravity environments is presented. The experimental apparatus consisted of a cylinder containing air as a fluid. The side wall of the cylinder was insulated while the bottom wall was allowed to remain at the ambient temperature. The enclosed air was rapidly heated by the top surface which consisted of a thin stainless steel foil connected to a battery pack as the power source. Thermocouples were used to measure the transient temperature of the air on the axis of the cylinder. The ouput of the thermocouples was displayed on digital thermometers and the temperature displays were recorded on film using a high-speed movie camera. Temperature measurements were obtained in the zero-gravity environment by dropping the apparatus in the 2-Seconds Zero-Gravity Drop Tower Facilities of NASA Lewis Research Center. In addition, experiments were also performed in the gravity environment and the results are compared in detail with those obtained under zero-gravity conditions.
Experimental observations of low and zero gravity nonlinear fluid-spacecraft interaction
1988-01-01
Low and zero gravity simulation experiments of the motion of a spacecraft coupled to the nonlinear slosh of a contained fluid are presented and discussed. A generic study model, in which a linear, spring-mass-damper spacecraft mode was coupled to the slosh of a fluid within an attached cylinder, has been studied experimentally using a unique, scale model apparatus. Low gravity
Fermionic zero modes in gauge and gravity backgrounds On $T^2$
Yi-Shi Duan; Yu-Xiao Liu; Yong-Qiang Wang
2006-03-12
In this note we study fermionic zero modes in gauge and gravity backgrounds taking a two dimensional compact manifold $T^2$ as extra dimensions. The result is that there exist massless Dirac fermions which have normalizable zero modes under quite general assumptions about these backgrounds on the bulk. Several special cases of gauge background on the torus are discussed and some simple fermionic zero modes are obtained.
Assessment of geophysical flows for zero-gravity simulation
C. B. Winn; A. Cox; R. Srivatsangam
1976-01-01
The results of research relating to the feasibility of using a low gravity environment to model geophysical flows are presented. Atmospheric and solid earth flows are considered. Possible experiments and their required apparatus are suggested.
Thermo-hydro-dynamic characteristics of a zero-gravity, spherical model of the troposphere
NASA Technical Reports Server (NTRS)
Srivatsangam, S.
1976-01-01
A model that exploits the radial inertia forces of a rotating fluid contained in a spherical annulus is described. The model would be flown in a satellite and experiments would be performed in very low or zero gravity. In such a model it would not be necessary to artificially simulate a radial gravity field. Thus small amounts of electrical energy would be sufficient to perform experiments. Since the only forces involved are thermo-hydro-dynamic ones, electromagnetic equations need not be considered.
Comprehensive Solution to the Cosmological Constant, Zero-Point Energy, and Quantum Gravity Problems
Philip D. Mannheim
2010-09-16
We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single comprehensive framework. We show that in quantum theories of gravity in which the zero-point energy density of the gravitational field is well-defined, the cosmological constant and zero-point energy problems solve each other by mutual cancellation between the cosmological constant and the matter and gravitational field zero-point energy densities. Because of this cancellation, regulation of the matter field zero-point energy density is not needed, and thus does not cause any trace anomaly to arise. We exhibit our results in two theories of gravity that are well-defined quantum-mechanically. Both of these theories are locally conformal invariant, quantum Einstein gravity in two dimensions and Weyl-tensor-based quantum conformal gravity in four dimensions (a fourth-order derivative quantum theory of the type that Bender and Mannheim have recently shown to be ghost-free and unitary). Central to our approach is the requirement that any and all departures of the geometry from Minkowski are to be brought about by quantum mechanics alone. Consequently, there have to be no fundamental classical fields, and all mass scales have to be generated by dynamical condensates. In such a situation the trace of the matter field energy-momentum tensor is zero, a constraint that obliges its cosmological constant and zero-point contributions to cancel each other identically, no matter how large they might be. Quantization of the gravitational field is caused by its coupling to quantized matter fields, with the gravitational field not needing any independent quantization of its own. With there being no a priori classical curvature, one does not have to make it compatible with quantization.
Middeck zero-gravity dynamics experiment - Comparison of ground and flight test data
Edward F. Crawley; Mark S. Barlow; Marthinus C. van Schoor; Brett Masters; Andrew S. Bicos
1992-01-01
An analytic and experimental study of the changes in the modal parameters of space structural test articles from one- to zero-gravity is presented. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension
A scaling analysis of thermoacoustic convection in a zero-gravity environment
Krane, R.J.; Parang, M.
1982-01-01
This paper presents a scaling analysis of a one-dimensional thermoacoustic convection heat transfer process in a zero-gravity environment. The relative importance of the terms in the governing equations is discussed for different time scales without attempting to solve the equations. The scaling analysis suggests certain generalizations that can be made in this class of heat transfer problems.
COMPUTATION OF THE FREE SURFACE FLOW OF A THIN LIQUID FILM AT ZERO AND NORMAL GRAVITY
M. M. Rahman; A. Faghri; W. L. Hankey; T. D. Swanson
1990-01-01
The results of numerical computations are presented for the free surface flow of a thin liquid film in the presence or absence of a gravitational body force. Three different flow systems were studied: a falling film down a vertical wall, plane and radial film flows under zero gravity, and plane and radial film flows along a horizontal plate in the
HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were assessed via classical time and frequency domain measures. Mean systolic and dias- tolic blood pressure
Two dimensional linear stability of premixed laminar flames under zero gravity
H. S. Mukunda; J. P. Drummond
1993-01-01
This paper reports on the numerical study of the linear stability of laminar premixed flames under zero gravity. The study specifically addresses the dependence of stability on finite rate chemistry with low activation energy and variable thermodynamic and transport properties. The calculations show that activation energy and details of chemistry play a minor role in altering the linear neutral stability
A zero-gravity instrument to study low velocity collisions of fragile particles at low temperatures
D. M. Salter; D. Heißelmann; G. Chaparro; G. van der Wolk; P. Reißaus; A. G. Borst; R. W. Dawson; E. de Kuyper; G. Drinkwater; K. Gebauer; M. Hutcheon; H. Linnartz; F. J. Molster; B. Stoll; P. C. van der Tuijn; H. J. Fraser; J. Blum
2009-01-01
We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for
Statistical support for the ATL program. [microbial growth in zero gravity
NASA Technical Reports Server (NTRS)
Hinkelmann, K.; Myers, R. H.
1976-01-01
Statistical experimental designs are presented for various numbers of organisms and agar solutions pertinent to the experiment, ""colony growth in zero gravity''. Missions lasting 7 and 30 days are considered. For the designs listed, the statistical analysis of the observations obtained on the space shuttle are outlined.
Dirac's point electron in the zero-gravity Kerr--Newman world
Michael K. -H. Kiessling; A. Shadi Tahvildar-Zadeh
2015-05-20
The results of a study of Dirac's Hamiltonian for a point electron in the zero-gravity Kerr--Newman spacetime are reported; here, "zero-gravity" means G to 0, where G is Newton's constant of universal gravitation, and the limit is effected in the Boyer--Lindquist coordinate chart of the maximal analytically extended, topologically nontrivial, Kerr--Newman spacetime. In a nutshell, the results are: the essential self-adjointness of the Dirac Hamiltonian; the reflection symmetry about zero of its spectrum; the location of the essential spectrum, exhibiting a gap about zero; and (under two smallness assumptions on some parameters) the existence of a point spectrum in this gap, corresponding to bound states of Dirac's point electron in the electromagnetic field of the zero-G Kerr--Newman ring singularity. The symmetry result of the spectrum extends to Dirac's Hamiltonian for a point electron in a generalization of the zero-G Kerr--Newman spacetime with different ratio of electric-monopole to magnetic-dipole moment. The results are discussed in the context of the general-relativistic Hydrogen problem. Also, some interesting projects for further inquiry are listed in the last section.
Criticality in the slowed-down boiling crisis at zero gravity
NASA Astrophysics Data System (ADS)
Charignon, T.; Lloveras, P.; Chatain, D.; Truskinovsky, L.; Vives, E.; Beysens, D.; Nikolayev, V. S.
2015-05-01
Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.
A study of immiscible liquids, liquid behavior at zero gravity, and dynamic contact lines and angles
NASA Astrophysics Data System (ADS)
Smedley, Gregory Todd
Three topics were investigated as part of preparation for a space based experiment. The intention of the experiment was to study the relationship between container geometry and interface geometry for a free liquid surface at zero gravity. A mathematical theory yields explicit geometrical criteria for the position of the free surface of a liquid at zero gravity in a cylindrical container of specified cross section. It is possible to find geometrical criteria that promise a particular liquid location. A unified graphical presentation of four geometries is given that can be used directly for the design of containments for liquids at zero gravity. As one application of these design curves, a container was built and tested in a series of two second drop-tower experiments. The identification of 121 transparent immiscible liquid pairs that have properties compatible with optical instrumentation based on laser-induced fluorescence is presented. Physical data such as specific gravity, index of refraction, viscosity, flash point, and toxicity were found in the literature. Compatibility with plexiglass (PMMA), contact angles of the internal meniscus on glass and PMMA, meniscus formation times, and clearing times were measured. A useful non-invasive for determining interfacial tensions is explained and used. The contact angle is a critical parameter in the consideration of liquid behavior at zero gravity; therefore, a technique based on laser light refraction was developed to objectively measure it. Dynamic contact line experiments were conducted at various velocities, both advancing and receding, using one of the 121 immiscible liquid pairs (nonane/formamide) in contact with glass.
Separation of biogenic materials by electrophoresis under zero gravity (L-3)
NASA Technical Reports Server (NTRS)
Kuroda, Masao
1993-01-01
Electrophoresis separates electrically charged materials by imposing a voltage between electrodes. Though free-flow electrophoresis is used without carriers such as colloids to separate and purify biogenic materials including biogenic cells and proteins in blood, its resolving power and separation efficiency is very low on Earth due to sedimentation, flotation, and thermal convection caused by the specific gravity differences between separated materials and buffer solutions. The objective of this experiment is to make a comparative study of various electrophoresis conditions on the ground and in zero-gravity in order to ultimately develop a method for separating various important 'vial' components which are difficult to separate on the ground.
NASA Technical Reports Server (NTRS)
Greco, R. V.; Eaton, L. R.; Wilkinson, H. C.
1974-01-01
The work is summarized which was accomplished from January 1974 to October 1974 for the Zero-Gravity Atmospheric Cloud Physics Laboratory. The definition and development of an atmospheric cloud physics laboratory and the selection and delineation of candidate experiments that require the unique environment of zero gravity or near zero gravity are reported. The experiment program and the laboratory concept for a Spacelab payload to perform cloud microphysics research are defined. This multimission laboratory is planned to be available to the entire scientific community to utilize in furthering the basic understanding of cloud microphysical processes and phenomenon, thereby contributing to improved weather prediction and ultimately to provide beneficial weather control and modification.
Flame spread over a thermally-thin solid fuel in zero gravity
F. C. Duh; C. H. Chen
1993-01-01
An analysis of flame spreading over a thin solid fuel in zero-gravity environment is presented. The mathematical model includes two-dimensional Navier-Stokes' momentum, energy and species equations with a one-step overall chemical reaction. The fuel consumption rate is described by a second-order Arrhenius kinetics. The energy balance along the solid fuel consists of the conduction, convection and radiation. The surface radiative
Anomalous heat transport by the piston effect in supercritical fluids under zero gravity
B. Zappoli; D. Bailly; Y. Garrabos; B. Le Neindre; P. Guenoun
1990-01-01
The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid (CO2) under zero gravity is studied by solving numerically the full nonlinear one-dimensional Navier-Stokes equations. Both short (acoustic) and long (diffusion) time scales are investigated. A new mechanism of heat transport is seen, where the thermal energy is transformed into kinetic energy in a hot expanding boundary
NASA Technical Reports Server (NTRS)
Dewitt, R. L.
1978-01-01
The preliminary concept, specifications, and requirements of a reusable zero gravity combustion facility (0-GCF) for use by experimenters aboard the spacelab payload of the space transportation system (STS) orbiter are described. The facility will be amenable to any mission of the STS orbiter in which a spacelab habitable segment and pallet segment are integral and for which orbital mission plans specify induced accelerations of 0.0001 g or less for sufficiently long periods so as not to impact experiment performance.
EVA Assembly of Large Space Structure Neutral Buoyancy, Zero-Gravity Simulation
NASA Technical Reports Server (NTRS)
1979-01-01
EVA Assembly of Large Space Structure Neutral Buoyancy, Zero-Gravity Simulation: NASA-LaRC Nestable Columns and Joints. The film depicts an extravehicular activity (EVA) that involved the assembly of six 'space-weight' columns into a regular tetrahedral cell by a team of two 'space'-suited test subjects. This cell represents the fundamental 'element' of a tetrahedral truss structure. The tests were conducted under simulated zero-gravity conditions, achieved by neutral buoyancy in water. The cell was assembled on an 'outrigger' assembly aid off the side of a mockup of the Shuttle Orbiter cargo bay. Both manual and simulated remote manipulator system (RMS) modes were evaluated. The simulated RMS was used only to transfer stowed hardware from the cargo bay to the work sites. Articulation limits of the pressure suit and zero gravity could be accommodated by work stations with foot restraints. The results of this study have confirmed that astronaut EVA assembly of large, erectable space structur is well within man's capabilities. [Entire movie available on DVD from CASI as Doc ID 20070031008. Contact help@sti.nasa.gov
Digital holographic microscopy for the cytomorphological imaging of cells under zero gravity
NASA Astrophysics Data System (ADS)
Toy, M. Fatih; Richard, Stephane; Kühn, Jonas; Franco-Obregón, Alfredo; Egli, Marcel; Depeursinge, Christian
2012-03-01
Digital holographic microscopy (DHM) has been gaining interest from cell biology community because of its label free nature and quantitative phase signal output. Besides, fast shutter time, image reconstruction by numerical propagation of the wave fields, and numerical compensation of the aberrations are other intrinsic advantages of this technique that can be explored for harsh imaging conditions. In the frame of this work, a transmission type DHM is developed with a decoupled epifluorescence microscopy mode for cytomorphological monitoring under zero gravity and hyper gravity. With the implemented automatic post processing routines, real time observation of the cell morphology is proven to be feasible under the influence of mechanical disturbances of zero gravity platforms. Post processing of holograms is composed from dynamic numerical compensation of holograms, robust autofocusing and phase image registration. Experiments on live myoblast cells are carried out on two different platforms; random positioning machine (RPM), a ground base microgravity simulation platform, and parabolic flight campaign (PFC), a fixed wing plane flight providing short durations of alternating gravity conditions. Results show clear perinuclear phase increase. During seconds scale microgravity exposure, measurable scale morphological modifications are observed with the accumulated effect of repetitive exposures and short breaks.
Berdahl, John P; Yu, Dao Yi; Morgan, William H
2012-12-01
Papilledema has long been associated with elevated intracranial pressure. Classically, tumors, idiopathic intracranial hypertension, and obstructive hydrocephalus have led to an increase in intracranial pressure causing optic nerve head edema and observable optic nerve swelling. Recent reports describe astronauts returning from prolonged space flight on the International Space Station with papilledema (Mader et al., 2011) [1]. Papilledema has not been observed in shorter duration space flight. Other recent work has shown that the difference in intraocular pressure (IOP) and cerebrospinal fluid pressure (CSFp) may be very important in the pathogenesis of diseases of the optic nerve, especially glaucoma (Berdahl and Allingham, 2009; Berdahl, Allingham, et al., 2008; Berdahl et al., 2008; Ren et al., 2009; Ren et al., 2011) [2-6]. The difference in IOP and CSFp across the lamina cribrosa is known as the translaminar pressure difference (TLPD). We hypothesize that in zero gravity, CSF no longer pools in the caudal spinal column as it does in the upright position on earth. Instead, CSF diffuses throughout the subarachnoid space resulting in a moderate but persistently elevated cranial CSF pressure, including the region just posterior to the lamina cribrosa known as the optic nerve subarachnoid space (ONSAS). This small but chronically elevated CSFp could lead to papilledema when CSFp is greater than the IOP. If the TLPD is the cause of optic nerve head edema in astronauts subjected to prolonged zero gravity, raising IOP and/or orbital pressure may treat this condition and protect astronauts in future space travels from the effect of zero gravity on the optic nerve head. Additionally, the same TLPD concept may offer a deeper understanding of the pathogenesis and treatment options of idiopathic intracranial hypertension (IIH), glaucoma and other diseases of the optic nerve head. PMID:22981592
A Photographic Study of Liquid Hydrogen Under Simulated Zero Gravity Conditions
NASA Technical Reports Server (NTRS)
Brazinsky, Irving; Weiss, Solomon
1962-01-01
The transient behavior of liquid hydrogen, under conditions of zero gravity, was studied photographically. The hydrogen was subjected to weightlessness by dropping a Dewar containing this liquid from a height of 9 feet. During the weightless period of approximately 3/4 second, the liquid rose along the walls of the Dewar into the original vapor space. The rise occurred at constant velocity for practically the entire duration of this period. Adhesive forces were concluded to be the primary cause of the liquid rise along the wall.
G. Quznetsov
2011-06-12
You shall not find any new physics, because all physical events are interpreted well-known particles (leptons, quarks, photons, gluons, W-bosons, Z-boson) and forces which have long known (electroweak, gravity, strong interactions). Contents: 1. Pointlike events and probability. 2. Leptons' moving equations and masses. 3. Fermion-antifermion asommetry. 4. Electroweak equations. 5. Chromatic states and gluons. 6. Asimptotic freedom, confinement, Newton's gravity. 7. Dark energy and dark matter. 8. Events and particles. 9. Conclusion.
Assessment of zero gravity effects on space worker health and safety
NASA Technical Reports Server (NTRS)
1980-01-01
One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.
Testing of a Spray-Bar Zero Gravity Cryogenic Vent System for Upper Stages
NASA Technical Reports Server (NTRS)
Lak, Tibor; Flachbart, Robin; Nguyen, Han; Martin, James
1999-01-01
The capability to vent in zero gravity without resettling is a fundamental technology need that involves practically all uses of subcritical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule- Thomson (J-T) valve to extract then-nal energy from the propellant. In a cooperative effort, Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (N4HTB) was used to test a unique "spray bar" TVS system developed by Boeing. A schematic of this system is included in Figure 1. The system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it radially into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the spray bar heat exchanger element, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. Figure 2 is a plot of ullage pressure (P4) and liquid vapor pressure (PSAI) versus time. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses. The primary advantage of the spray bar configuration is that pressure reduction is achieved independent of liquid and vapor location, thereby enhancing the applicability of normal gravity test data to zero gravity conditions. The in-tank components are minimized with the proposed TVS design. Because the recirculation pump is external to the tank, no electrical power penetration of the tank is required for pump or valve operation. This is especially desirable for L02 tanks since the presence of an electrical ignition source in oxygen represents a critical failure mode. Also, since the critical components (pump, motor, valve, orifice) are external to the tank, system checkout and ground servicing/replacement are easier. For zero-g operation, component replacement external to the tank may be a significant benefit. In addition to satisfying the zero g TVS design objectives, the TVS concept tested offers additional benefits to the integrated subcritical cryogenic storage and launch system.
Design, fabrication and acceptance testing of a zero gravity whole body shower
NASA Technical Reports Server (NTRS)
Schumacher, E. A.; Lenda, J. A.
1974-01-01
Recent research and development programs have established the ability of the zero gravity whole body shower to maintain a comfortable environment in which the crewman can safely cleanse and dry the body. The purpose of this program was to further advance the technology of whole body bathing and to demonstrate technological readiness including in-flight maintenance by component replacement for flight applications. Three task efforts of this program are discussed. Conceptual designs and system tradeoffs were accomplished in task 1. Task 2 involved the formulation of preliminary and final designs for the shower, while task 3 included the fabrication and test of the shower assembly. Particular attention is paid to the evaluation and correction of test anomalies during the final phase of the program.
Human physiological problems in zero gravity - An attempt at understanding through systems analysis
NASA Technical Reports Server (NTRS)
White, R. J.; Croston, R. C.
1974-01-01
When the experimental situation is that of man exposed to a gravitationless environment for varying periods of time, the possible importance and value of a related modeling effort is readily apparent. One of the main objectives of the Skylab Program, with its missions of 28, 59, and 85 day duration concerned biomedical investigations of various types, and large amounts of relevant experimental data have been gathered and are in the process of being sorted and interpreted. In order to be of eventual usefulness in forming and testing consistent physiological hypotheses concerning the effect of zero gravity on man, a modeling effort was established in 1972 through the General Electric Company, Space Division, Houston, Texas. An account is given of some of the developments completed or in progress as part of this modeling effort. A long-term cardiovascular model and a large model of the systemic circulation are discussed.
A zero-gravity instrument to study low velocity collisions of fragile particles at low temperatures.
Salter, D M; Heisselmann, D; Chaparro, G; van der Wolk, G; Reissaus, P; Borst, A G; Dawson, R W; de Kuyper, E; Drinkwater, G; Gebauer, K; Hutcheon, M; Linnartz, H; Molster, F J; Stoll, B; van der Tuijn, P C; Fraser, H J; Blum, J
2009-07-01
We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for a total of 2.4 h in reduced-gravity conditions and successfully recording over 300 separate collisions of loosely packed dust aggregates and ice samples. The imparted particle velocities achieved range from 0.03 to 0.28 m s(-1) and a high-speed, high-resolution camera captures the events at 107 frames/s from two viewing angles separated by either 48.8 degrees or 60.0 degrees. The particles can be stored inside the experiment vacuum chamber at temperatures of 80-300 K for several uninterrupted hours using a built-in thermal accumulation system. The copper structure allows cooling down to cryogenic temperatures before commencement of the experiments. Throughout the parabolic flight campaigns, add-ons and modifications have been made, illustrating the instrument flexibility in the study of small particle collisions. PMID:19655969
A zero-gravity instrument to study low velocity collisions of fragile particles at low temperatures
NASA Astrophysics Data System (ADS)
Salter, D. M.; Heißelmann, D.; Chaparro, G.; van der Wolk, G.; Reißaus, P.; Borst, A. G.; Dawson, R. W.; de Kuyper, E.; Drinkwater, G.; Gebauer, K.; Hutcheon, M.; Linnartz, H.; Molster, F. J.; Stoll, B.; van der Tuijn, P. C.; Fraser, H. J.; Blum, J.
2009-07-01
We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for a total of 2.4 h in reduced-gravity conditions and successfully recording over 300 separate collisions of loosely packed dust aggregates and ice samples. The imparted particle velocities achieved range from 0.03 to 0.28 m s-1 and a high-speed, high-resolution camera captures the events at 107 frames/s from two viewing angles separated by either 48.8° or 60.0°. The particles can be stored inside the experiment vacuum chamber at temperatures of 80-300 K for several uninterrupted hours using a built-in thermal accumulation system. The copper structure allows cooling down to cryogenic temperatures before commencement of the experiments. Throughout the parabolic flight campaigns, add-ons and modifications have been made, illustrating the instrument flexibility in the study of small particle collisions.
A Zero-Gravity Instrument to Study Low Velocity Collisions of Fragile Particles at Low Temperatures
Salter, D M; Chaparro, G; van der Wolk, G; Reißaus, P; Borst, A G; Dawson, R W; de Kuyper, E; Drinkwater, G; Gebauer, K; Hutcheon, M; Linnartz, H; Molster, F J; Stoll, B; van der Tuijn, P C; Fraser, H J; Blum, J
2009-01-01
We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for a total of 2.4 hours in reduced gravity conditions and successfully recording over 300 separate collisions of loosely packed dust aggregates and ice samples. The imparted particle velocities achieved range from 0.03-0.28 m s^-1 and a high-speed, high-resolution camera captures the events at 107 frames per second from two viewing angles separated by either 48.8 or 60.0 degrees. The particles can be stored inside the experiment vacuum chamber at temperatures of 80-300 K for several uninterrupted hours using a built-in thermal accumulation system. The copper structure allows cooling down to cryogenic temper...
Transient boiling heat transfer in saturated liquid nitrogen and F113 at standard and zero gravity
NASA Technical Reports Server (NTRS)
Oker, E.; Merte, H., Jr.
1973-01-01
Transient and steady state nucleate boiling in saturated LN2 and F113 at standard and near zero gravity conditions were investigated for the horizontal up, vertical and horizontal down orientations of the heating surface. Two distinct regimes of heat transfer mechanisms were observed during the interval from the step increase of power input to the onset of nucleate boiling: the conduction and convection dominated regimes. The time duration in each regime was considerably shorter with LN2 than with F113, and decreased as heat flux increased, as gravity was reduced, and as the orientation was changed from horizontal up to horizontal down. In transient boiling, boiling initiates at a single point following the step increase in power, and then spreads over the surface. The delay time for the inception of boiling at the first site, and the velocity of spread of boiling varies depending upon the heat flux, orientation, body force, surface roughness and liquid properties, and are a consequence of changes in boundary layer temperature levels associated with changes in natural convection. Following the step increase in power input, surface temperature overshoot and undershoot occur before the steady state boiling temperature level is established.
NASA Technical Reports Server (NTRS)
Musacchia, X. J.
1974-01-01
Pathophysiological conditions resulting from prolonged exposure to zero gravity, cabin constraint, altered ambient environment, whether it be noise, vibrations, high temperatures, or combinations of such factors, are studied in laboratory animals and applied to manned space flight. Results and plans for further study are presented. Specific topics covered include: thermoregulation and its role in reflecting stress and adaptation to the gravity free environment and cabin confinement with its altered circadian forcings; renal function and its measurement in electrolyte distribution and blood flow dynamics; gastronintestinal function and an assessment of altered absorptive capacity in the intestinal mucosa; and catecholamine metabolism in terms of distribution and turnover rates in specific tissues.
Spray Bar Zero-Gravity Vent System for On-Orbit Liquid Hydrogen Storage
NASA Technical Reports Server (NTRS)
Hastings, L. J.; Flachbart, R. H.; Martin, J. J.; Hedayat, A.; Fazah, M.; Lak, T.; Nguyen, H.; Bailey, J. W.
2003-01-01
During zero-gravity orbital cryogenic propulsion operations, a thermodynamic vent system (TVS) concept is expected to maintain tank pressure control without propellant resettling. In this case, a longitudinal spray bar mixer system, coupled with a Joule-Thompson (J-T) valve and heat exchanger, was evaluated in a series of TVS tests using the 18 cu m multipurpose hydrogen test bed. Tests performed at fill levels of 90, 50, and 25 percent, coupled with heat tank leaks of about 20 and 50 W, successfully demonstrated tank pressure control within a 7-kPa band. Based on limited testing, the presence of helium constrained the energy exchange between the gaseous and liquid hydrogen (LH2) during the mixing cycles. A transient analytical model, formulated to characterize TVS performance, was used to correlate the test data. During self-pressurization cycles following tank lockup, the model predicted faster pressure rise rates than were measured; however, once the system entered the cyclic self-pressurization/mixing/venting operational mode, the modeled and measured data were quite similar. During a special test at the 25-percent fill level, the J-T valve was allowed to remain open and successfully reduced the bulk LH2 saturation pressure from 133 to 70 kPa in 188 min.
Effects of zero gravity on myofibril content and isomyosin distribution in rodent skeletal muscle
NASA Technical Reports Server (NTRS)
Baldwin, K. M.; Herrick, R. E.; Ilyina-Kakueva, E.; Oganov, V. S.
1990-01-01
The purpose of this experiment was to investigate the effects of 12.5 days of zero gravity (0 g) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n = 5 each group) designated as flight group (FG), vivarium control (VC), and synchronous control (SC). Body weight of the FG was significantly lower than that of the two control groups (P less than 0.05). Compared with the two control groups, VI weight was lower by 23% (P less than 0.10), whereas no such pattern was apparent for the VL muscle. Myofibril yields (mg protein/g muscle) in the VI were 35% lower in the FG than in controls (P less than 0.05), whereas no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0 g. Analysis of myosin isoforms indicated that slow myosin (Sm) was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following spaceflight. Myofibril ATPase activity of the VI was increased in the FG compared with controls, which is consistent with the observation of preferential Sm degradation. These data suggest that muscles containing a high percentage of slow-twitch fibers undergo greater degrees of myofibril protein degradation than muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0 g exposure, and the primary target appears to be the Sm molecule.
N-Decane-Air Droplet Combustion Experiments in the NASA-Lewis 5 Second Zero-Gravity Facility
NASA Technical Reports Server (NTRS)
Haggard, John B.; Brace, Michael H.; Dryer, Frederick L.; Choi, Mun Y.; Williams, Forman A.
1990-01-01
The burning of single fuel (n-decane) droplets in a microgravity environment (below 0.00001 of the earth's gravity, achieved in the NASA-Lewis 5-Second Zero-Gravity Facility) was studied, as part of the development of the Droplet Combustion Experiment for eventual operation aboard either the Shuttle middeck or Spacelab. Special attention is given to the combustion equipment used and its operations and performance. Temporal analysis of the local burning rates in these tests showed increasing rates of change in the local burning as droplet combustion progressed. Result point to the need of studying large droplets, with long droplet combustion lifetimes as well as low gas/droplet motion to understand reasons for this unsteadiness.
Hill, Richard J. A.; Larkin, Oliver J.; Dijkstra, Camelia E.; Manzano, Ana I.; de Juan, Emilio; Davey, Michael R.; Anthony, Paul; Eaves, Laurence; Medina, F. Javier; Marco, Roberto; Herranz, Raul
2012-01-01
Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396
Hill, Richard J A; Larkin, Oliver J; Dijkstra, Camelia E; Manzano, Ana I; de Juan, Emilio; Davey, Michael R; Anthony, Paul; Eaves, Laurence; Medina, F Javier; Marco, Roberto; Herranz, Raul
2012-07-01
Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396
NASA Technical Reports Server (NTRS)
Smedley, G.
1990-01-01
Plexiglass containers with rounded trapezoidal cross sections were designed and built to test the validity of Concus and Finn's existence theorem (1974, 1983) for a bounded free liquid surface at zero gravity. Experiments were carried out at the NASA Lewis two-second drop tower. Dyed ethanol-water solutions and three immiscible liquid pairs, with one liquid dyed, were tested. High-speed movies were used to record the liquid motion. Liquid rose to the top of the smaller end of the containers when the contact angle was small enough, in agreement with the theory. Liquid interface motion demonstrated a strong dependence on physical properties, including surface roughness and contamination.
The Dirac point electron in zero-gravity Kerr-Newman spacetime
NASA Astrophysics Data System (ADS)
Kiessling, M. K.-H.; Tahvildar-Zadeh, A. S.
2015-04-01
Dirac's wave equation for a point electron in the topologically nontrivial maximal analytically extended electromagnetic Kerr-Newman spacetime is studied in a limit G ? 0, where G is Newton's constant of universal gravitation. The following results are obtained: the formal Dirac Hamiltonian on the static spacelike slices is essentially self-adjoint and the spectrum of the self-adjoint extension is symmetric about zero, featuring a continuum with a gap about zero that, under two smallness conditions, contains a point spectrum. The symmetry result extends to the Dirac operator on a generalization of the zero-G Kerr-Newman spacetime with different electric-monopole/magnetic-dipole-moment ratios.
Combustion of solid carbon rods in zero and normal gravity. Ph.D. Thesis - Toledo Univ., Ohio
NASA Technical Reports Server (NTRS)
Spuckler, C. M.
1981-01-01
In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.
Modeling and control of the pneumatic constant pressure system for zero gravity simulation
Bo Lu; Guoliang Tao; Zhong Xiang; Wei Zhong
2008-01-01
This paper presents a complete dynamic model and a hybrid design method for the high precision pneumatic constant pressure control system for a gravity compensation suspension device. The pneumatic system components consist of newly-developed frictionless cylinders without mechanical seals, a large tank and an electro-pneumatic proportional pressure valve. The complete mathematical models are derived, which consist of valve dynamics and
Manual control in space research on perceptual-motor functions under zero gravity conditions (L-10)
NASA Technical Reports Server (NTRS)
Tada, Akira
1993-01-01
Are human abilities to control vehicles and other machines the same in space as those on Earth? The L-10 Manual Control Experiment of the First Materials Processing Tests (FMPT) started from this question. Suppose a pilot has the task to align the head of a space vehicle toward a target. His actions are to look at the target, to determine the vehicle movement, and to operate the manipulator. If the activity of the nervous system were the same as on Earth, the movements, of the eye and hand would become excessive because the muscles do not have to oppose gravity. The timing and amount of movement must be arranged for appropriate actions. The sensation of motion would also be affected by the loss of gravity because the mechanism of the otolith, the major acceleration sensor, depends on gravity. The possible instability of the sensation of direction may cause mistakes in the direction of control of manipulator movement. Thus, the experimental data can be used for designing man-machine systems in space, as well as for investigation of physiological mechanisms. In this experiment, the direction of vehicle heading is expressed by a light spot on an array of light emitting diodes and the manipulator is of a finger stick type. As the light spot moves up and down, the Japanese Payload Specialist, and the subject, must move the manipulator forward and backward to keep the movement of the light spot within the neighborhood of the central point of the display. The position of the light spot is computed in such a manner that when the stick is kept at the neutral position, a motion whose acceleration is proportional to the angle of deflection is added to the movement of the light spot. The Operator Describing Function, which is an expression of human control characteristics, can be calculated from 2 minutes of raw data of the light spot position and stick deflection. The 2 minutes of operation is called a run, and 8 runs with resting periods composes a session. The on-orbit experiment will be conducted on the second, fourth, and seventh days. One session of experiment of each of these days is conducted following the L-4 experiment, which uses the same apparatus. The Payload Specialist, aided by a Mission Specialist, will take our apparatus from a rack container, set up the apparatus, attach electrodes for measurements of eye movement and muscle activity, conduct the L-4 Visual Stability Experiment, conduct one session of the manual control experiment, and then dissemble and stow the apparatus. In addition to the flight experiment, pre-flight and post-flight experiments will be conducted. The data of three sessions on orbit will reflect adaption of physiological systems to microgravity. The data of post-flight experiments, on the other hand, will reflect re-adaptation of physiological systems to the gravity condition on the ground. Control data collected with and without psychological tension will be scheduled just prior to and long before launch.
NASA Technical Reports Server (NTRS)
Tipton, Charles M.
1991-01-01
The primary purpose of this research is to study the physiological mechanisms associated with the exercise performance of rats subjected to conditions of simulated weightlessness. A secondary purpose is to study related physiological changes associated with other systems. To facilitate these goals, a rodent suspension model was developed (Overton-Tipton) and a VO2 max testing procedure was perfected. Three methodological developments occurred during this past year deserving of mention. The first was the refinement of the tail suspension model so that (1) the heat dissipation functions of the caudal artery can be better utilized, and (2) the blood flow distribution to the tail would have less external constriction. The second was the development on a one-leg weight bearing model for use in simulated weightlessness studies concerned with change in muscle mass, muscle enzyme activity, and hind limb blood flow. The chemical body composition of 30 rats was determined and used to develop a prediction equation for percent fat using underwater weighing procedures to measure carcass specific gravity and to calculate body density, body fat, and fat free mass.
NASA Astrophysics Data System (ADS)
Struckmeier, Jens; Tenbosch, Jochen; Klopp, Erk; Born, Matthias; Hofmann, Martin R.; Jones, David B.
2000-04-01
We introduce a compact and portable photometric system for measurements of the calcium dynamics in cells. The photometer is designed for applications in centrifuges or in zero-gravity environment and thus extremely compact and reliable. It operates with the calcium-sensitive dye Indo-1. The excitation wavelength of 345nm is generated by frequency doubling of a laser diode. Two compact photomultiplier tubes detect the fluorescent emission. The electronics provides the sensitivity of photon counting combined with simultaneous measurement of the temperature, of air pressure, and of gravitational force. Internal data storage during the experiment is possible. A newly developed cell chamber stabilizes the cell temperature to 37.0 percent C +/- 0.1 degree C and includes a perfusion system to supply the cells with medium. The system has a modular set-up providing the possibility to change light source and detectors for investigation of other ions than calcium. Quantitative measurements of the intracellular calcium concentration are based on a comprehensive calibration of our system. First experiments show that the calcium dynamics of osteosarcoma cells stimulated by parathyroid hormone is observable.
NSDL National Science Digital Library
Ms. Hendricks
2007-11-06
3rd Grade Science Standard 4: Students will understand that objects near Earth are pulled toward Earth by gravity Objective 2: Describe the effects of gravity on the motion of an object In this activity we will learn how gravity effects the motion of an object. We will do this by finding out what gravity is and watching experiments on gravity. Finally, we will conduct our own experiment to see first hand how gravity effects everything around us. So, what is gravity? Is it a term that you have heard before? What does it do? Why is it so important? Why do we need to know how it works? If you\\'ve ever wondered what the answers to these questions are, then you\\'re in ...
NASA Astrophysics Data System (ADS)
Kozlova, Tatiana; Karol Seweryn, D..; Grygorczuk, Jerzy; Kozlov, Oleg
The sample return missions have made a very significant progress to understanding of geology, the extra-terrestrial materials, processes occurring on surface and subsurface level, as well as of interactions between such materials and mechanisms operating there. The various sample return missions in the past (e.g. Apollo missions, Luna missions, Hayabusa mission) have provided scientists with samples of extra-terrestrial materials allowing to discover answers to critical scientific questions concerning the origin and evolution of the Solar System. Several new missions are currently planned: sample return missions, e.g Russian Luna-28, ESA Phootprint and MarcoPolo-R as well as both robotic and manned exploration missions to the Moon and Mars. One of the key challenges in such missions is the reliable sampling process which can be achieved by using many different techniques, e.g. static excavating technique (scoop), core drilling, sampling using dynamic mechanisms (penetrators), brushes and pneumatic systems. The effectiveness of any sampling strategy depends on many factors, including the required sample size, the mechanical and chemical soil properties (cohesive, hard or porous regolith, stones), the environment conditions (gravity, temperature, pressure, radiation). Many sampling mechanism have been studied, designed and built in the past, two techniques to collect regolith samples were chosen for the Phobos-Grunt mission. The proposed system consisted of a robotic arm with a 1,2m reach beyond the lander (IKI RAN); a tubular sampling device designed for collecting both regolith and small rock fragments (IKI RAN); the CHOMIK device (CBK PAN) - the low velocity penetrator with a single-sample container for collecting samples from the rocky surface. The functional tests were essential step in robotic arm, sampling device and CHOMIK device development process in the frame of Phobos-Grunt mission. Three major results were achieved: (i) operation scenario for autonomous sampling; (ii) technical characteristics of both devices, i.e. progress cycles of CHOMIK device in different materials and torque in the manipulator joints during sampling operations; (iii) confirmation of applicability of both devices to perform such type of tasks. The phases in operational scenario were prepared to meet mission and system requirements mainly connected with: (i) environment (near zero gravity, vacuum, dust), (ii) safety and (iii) to avoid common operation of both devices at the same time.
NASA Technical Reports Server (NTRS)
Gatos, H. C.; Witt, A. F.; Lichtensteiger, M.; Herman, C. J.
1982-01-01
The crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero g conditions were investigated. The germanium (doped with gallium) system was selected because it was extensively studied on Earth and because it lends itself to a very detailed macroscopic and microscopic characterization. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. On the basis of the results obtained to date, there is no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.
Zero gravity two-phase flow regime transition modeling compared with data and relap5-3d predictions
Ghrist, Melissa Renee
2009-05-15
like to thank all of the people at NASA who encourage reduced gravity research. Lastly I would like to thank my friends and family who have encouraged and believed in me. I know I would have never been able to get as far as I have without every... data compared with the amount of 1-g data due partially to the fact that data are difficult to collect. There has been work done collecting reduced gravity data aboard NASA?s reduced gravity aircraft, the space shuttle, and International Space...
Liouville gravity from Einstein gravity
D. Grumiller; R. Jackiw
2007-12-28
We show that Liouville gravity arises as the limit of pure Einstein gravity in 2+epsilon dimensions as epsilon goes to zero, provided Newton's constant scales with epsilon. Our procedure - spherical reduction, dualization, limit, dualizing back - passes several consistency tests: geometric properties, interactions with matter and the Bekenstein-Hawking entropy are as expected from Einstein gravity.
NASA Technical Reports Server (NTRS)
Phillips, Warren F.
1989-01-01
The results obtained show that it is possible to control light-weight robots with flexible links in a manner that produces good response time and does not induce unacceptable link vibrations. However, deflections induced by gravity cause large static position errors with such a control system. For this reason, it is not possible to use this control system for controlling motion in the direction of gravity. The control system does, on the other hand, have potential for use in space. However, in-space experiments will be needed to verify its applicability to robots moving in three dimensions.
NASA Technical Reports Server (NTRS)
Haggard, John B.; Borowski, Brian A.; Dryer, Frederick L.; Choi, Mun Y.; Williams, Forman A.
1991-01-01
The burning rate of single droplets of n-decane in a microgravity environment of the NASA-Lewis 5 Second Zero-Gravity Facility was investigated as a function of time, together with the flame diameter/droplet diameter ratio, for a wide range of test environments other than normal air conditions, using an engineering model of the flight experiment. Oxygen mole fractions were varied from 18 to 50 percent, the total test chamber pressure was varied from 0.5 to 2 atmospheres, and the initial droplet diameter was varied from 0.98 to 2.41 mm. Measurements showed that the average burning rates for n-decane droplets exhibited the same qualitative trends as are found in two current models. Temporal analysis of the local burning rates showed variable rates of change in local burning as the droplet combustion progressed. The causes and implications of these findings are discussed.
Zero-gravity Mean Free Surface Curvature of a Confined Liquid in a Radially-Vaned Container
NASA Technical Reports Server (NTRS)
Chen, Yongkang; Callahan, Michael; Weislogel, Mark
2013-01-01
A variety of increasingly intricate container geometries are under consideration for the passive manipulation of liquids aboard spacecraft where the impact of gravity may be neglected. In this study we examine the mean curvature of a liquid volume confined within a radial array of disconnected vanes of infinite extent. This particular geometry possesses a number of desirable characteristics relevant to waste water treatment aboard spacecraft for life support. It is observed that under certain conditions the slender shape of the free surface approaches an asymptote, which can be predicted analytically using new hybrid boundary conditions proposed herein. This contribution represents possibly the final extension of what has been referred to as the method of de Lazzer et al. (1996). The method enables the integration of the Young-Laplace equation over a domain with its boundaries, including the wetted portion of the solid boundaries, symmetry planes, and circular arcs representing free surfaces at the center plane of the liquid body. Asymptotic solutions at several limits are obtained and the analysis is confirmed with numerical computations.
NASA Astrophysics Data System (ADS)
Xu, Peiliang
2015-04-01
Satellite orbits have been routinely used to produce models of the Earth's gravity field. The numerical integration method is most widely used by almost all major institutions to determine standard gravity models from space geodetic measurements. As a basic component of the method, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this talk, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, setting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies. To conclude, the numerical integration method, as is widely used today by major institutions to produce standard satellite gravity models, is simply incorrect mathematically. As a direct consequence, further work is required to confirm whether the numerical integration method can still be used as a mathematical foundation to produce standard satellite gravity models. More details can be found in Xu (2009, Sci China Ser D-Earth Sci, 52, 562-566).
P. Karmakar; Greeninavin
2010-01-01
Space travelling is not possible for human because, by the time, we cross Jupiter, our bones dissolve as there is zero gravity and, by developing a gravity chamber in the space ship itself we will be able to travel in space for generations and explore the universe.
NASA Technical Reports Server (NTRS)
Barnett, R. D.; Gowen, R. J.; Carroll, D. R.
1975-01-01
The cardiovascular responses of the Apollo crewmen associated with postflight evaluations indicate varying decrements of orthostatic tolerance. The postflight changes indicate a slightly diminished ability to the cardiovascular system to function effectively against gravity following exposure to weightlessness. The objective of the Skylab LBNP experiments (M092) was to provide information about the magnitude and time course of the cardiovascular changes associated with prolonged periods of exposure to weightlessness. This report details the equipment, signal processing and analysis of the leg volume data obtained from the M092 experiment of the Skylab 3 Mission.
GENERAL RELATIVITY AND THE ZERO POINT ENERGY
Barry Setterfield
2001-01-01
An exploration is made of the stochastic electrodynamic (SED) interpretation of mass and gravity. On this approach, gravity has been shown to originate in the attractive secondary electromagnetic fields emitted by charged point particles jostled by the impacting waves of the Zero Point Energy (ZPE). This exploration finds that the four major predictions of General Relativity can be readily reproduced
NSDL National Science Digital Library
Joe Szewczyk
2012-06-26
The definition of the Zero Property of Multiplication will be presented and discussed, along with a review of other vocabulary necessary for this lesson (factors, products, "groups of", Commutative Property). The students will be taken through a guided lesson, showing them and explaining to them the process of multiplying by 0. This will be followed by independent practice for the students, including a peer review of said practice. The lesson will conclude with a whole class review of the Zero Property of Multiplication. At each step along the way, the teacher will be monitoring student progress and decide on a reteaching worksheet, continued independent practice, or an enrichment exercise.
Othman Ahmad; Aroland Kiring; Ali Chekima
2012-10-17
It is fundamentally possible to travel with zero energy based on Newton Laws of Motion. According to the first law of motion, a body will continue to travel for infinite distance unless it is acted upon by another force. For a body in motion, the force which stops perpetual motion is friction. However, there are many circumstances that friction is zero, for example in space, where there is vacuum. On earth, gravity makes objects to be in constant contact with each other generating friction but technology exists to separate them in the air using powerful magnetic forces. At low speeds, the friction caused by air is minimal but we can create vacuum even on land for high speed travel. Another condition for travelling is for it to stop at its destination. On land, we can recover the kinetic energy back into electrical energy using brushless permanent magnet generators. These generators can also convert electric energy into kinetic energy in order to provide motion. This article reviews technologies that will allow us to travel with zero energy. It is easier to do it on land but in the air, it is not obvious.
APOLLO 8: It's Christmas in zero gravity...
NASA Technical Reports Server (NTRS)
1974-01-01
Astronauts and ground control consider how Santa is going to gain access to the command module... From the film documentary 'APOLLO 8:'Debrief': part of a documentary series made in the early 70's on the APOLLO missions, and narrated by Burgess Meredith. (Actual date created is not known at this time) First manned Saturn V flight with Frank Borman, James A. Lovell, Jr.,and william A. Anders. First manned lunar orbit mission; provided a close-up look at the moon during 10 lunar orbits. Mission Duration 147hrs 0m 42s
NASA Astrophysics Data System (ADS)
Masters, Roy
2007-03-01
Einstein's cosmological constant as gravity, will unify quantum mechanics to general relativity and link gravity to electromagnetism. Then, an electromagnetic vacuum engine driven by the force that spins, moves, and sustains mass at the subatomic level, will do free, what generators cannot. Flowing outward-bound sinusoidally from its source, this gravity force assumes a three-dimensional spherical universe. Lines of force intersect, spinning into gyroscopic particles and passes as time-present, with a compression gravity of space-time curvature continuum unifying all mass. The spaces between approaching masses suffer a decrease of right-angled vacuum energy, increasing external pressures, pushing them together. Ubiquitous gravity now interacts electromagnetically with mass. Gravity's ``heat energy'' operates below absolute zero and squeezes mass into thermonuclear ignition of stars. Creation needs a gravity field for the propagation of light that will make sense of its wave/particle behavior. Creation from a white hole recycles down through a black one, into new beginnings of galaxies. ``Vacuum energy'' will light cities and factories; faster than light spacecraft will raise silently from the ground utilizing the very gravity it defies, propelling us to the stars.
Workplace Justice, Zero Tolerance, Zero Barriers
Workplace Justice, Zero Tolerance, and Zero Barriers Š2001 Mary Rowe, PhD Massachusetts Institute attempting to prevent illegal behavior and to control various kinds of costs. Many have established "zero extent in conflict because many employers have interpreted zero tolerance to require mandatory punishment
ERIC Educational Resources Information Center
Anthony, Glenda J.; Walshaw, Margaret A.
2004-01-01
This article discusses the challenges students face in making sense of zero as a number. A range of different student responses to a computation problem involving zero reveal students' different understandings of zero.
Structural zeroes and zero-inflated models
HE, Hua; TANG, Wan; WANG, Wenjuan; CRITS-CHRISTOPH, Paul
2014-01-01
Summary In psychosocial and behavioral studies count outcomes recording the frequencies of the occurrence of some health or behavior outcomes (such as the number of unprotected sexual behaviors during a period of time) often contain a preponderance of zeroes because of the presence of structural zeroes that occur when some subjects are not at risk for the behavior of interest. Unlike random zeroes (responses that can be greater than zero, but are zero due to sampling variability), structural zeroes are usually very different, both statistically and clinically. False interpretations of results and study findings may result if differences in the two types of zeroes are ignored. However, in practice, the status of the structural zeroes is often not observed and this latent nature complicates the data analysis. In this article, we focus on one model, the zero-inflated Poisson (ZIP) regression model that is commonly used to address zero-inflated data. We first give a brief overview of the issues of structural zeroes and the ZIP model. We then given an illustration of ZIP with data from a study on HIV-risk sexual behaviors among adolescent girls. Sample codes in SAS and Stata are also included to help perform and explain ZIP analyses. PMID:25317011
Brane worlds in critical gravity
NASA Astrophysics Data System (ADS)
Chen, Feng-Wei; Liu, Yu-Xiao; Zhong, Yuan; Wang, Yong-Qiang; Wu, Shao-Feng
2013-11-01
Recently, Lü and Pope proposed critical gravities in [Phys. Rev. Lett. 106, 181302 (2011)]. In this paper we construct analytic brane solutions in critical gravity with matter. The Gibbons-Hawking surface term and junction condition are investigated, and the thin and thick brane solutions are obtained. All these branes are embedded in five-dimensional anti-de Sitter spacetimes. Our solutions are stable against scalar perturbations, and the zero modes of scalar perturbations cannot be localized on the branes.
Passive and Active Stabilization of Liquid Bridges in Low Gravity
David B. Thiessen; Wei Wei; Philip L. Marston
2002-01-01
The cylindrical liquid bridge of arbitrary size surrounded by air or vacuum is a fluid configuration that is essentially unique to the zero-gravity environment. An associated technology, which is enhanced in zero gravity, is the float-zone process of crystal growth, which involves a molten liquid bridge between a feed rod and the growing cylindrical crystal. There are several advantages to
Cynthia Dlvork; Moni Naori; Amit Sahai
1998-01-01
Concurrent executions of a zero-knowledge protocol by asingle prover (with one or more verifiers) may leak informationand may not be zero-knowledge in toto; for example, inthe case of zero-knowledge interactive proofs or arguments,the interactions remain proofs but may fail to remain zeroknowledge.This paper addresses the problem of achievingconcurrent zero-knowledge.We introduce timing in order to obtain zero-knowledgein concurrent executions. We assume
Atmospheric Science Data Center
2013-04-19
article title: Gravity Waves Ripple over Marine Stratocumulus Clouds ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ...
Zero Zeros After All These (20) Years
U. Baur; R. Brown
1999-09-27
We celebrate two birthdays connected with the radiation zero phenomenon. First, a striking dip in the theoretical angular distributions of radiative weak-boson production was discovered twenty years ago. The key experimental interest is that this will not occur in any deviation from the standard model. Second, the classical training of Stanley Brodsky began sixty years ago, which was instrumental in understanding why theoretical spin-independent radiation zeros appear in almost all Born amplitudes for the radiation of photons and gluons and other massless gauge bosons (but rarely in physical kinematic regions). And there are approximate zeros for massive bosons and ``Type II'' zeros that can also be studied. We discuss how the difficulties in observing the original Mikaelian-Samuel-Sahdev zero finally may be surmounted next year.
Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li
Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li Gravity contrast that gives rise to zero gravity response on the surface. As a result, part of the salt structure structure using gravity data can be divided into two general categories. The first are interface inversions
ERIC Educational Resources Information Center
Henault, Cherry
2001-01-01
Questions the effectiveness of the widespread use of zero-tolerance policies enacted by school boards to punish students who violate weapon and drug rules. Suggests that enforcement of zero-tolerance policies has not been equitable. Reviews proposal for alternative to zero tolerance. (PKP)
NASA Technical Reports Server (NTRS)
Williams, F. A.
1978-01-01
Questions of the importance and feasibility of performing experiments on droplet burning at zero gravity in Spacelab were studied. Information on the physics and chemistry of droplet combustion, with attention directed specifically to the chemical kinetics, heat and mass transfer, and fluid mechanics of the phenomena involved, are presented. The work was divided into three phases, the justification, the feasibility, and the conceptual development of a preliminary design. Results from the experiments performed revealed a few new facts concerning droplet burning, notably burning rates in excess of theoretical prediction and a phenomenon of flash extinction, both likely traceable to accumulation of carbon produced by gas-phase pyrolysis in the fuel-rich zone enclosed by the reaction surface. These experiments also showed that they were primarily due to timing difficulties.
NSDL National Science Digital Library
Arsham, Hossein.
We have heard of calling someone "a total zero" as an insult, but what does "zero" really mean? This thoughtful and informative Website from Dr. Hossein Arsham, Wright Distinguished Research Professor of Statistics and Management Science at the University of Baltimore, discusses the history and philosophy of zero. Items presented include arguments for and against dividing by zero, the ideas of zero as a void and as a number, zero in limits, square roots, and divergent series and floating points. The text is peppered with links to related mathematics, computer science, and history of mathematics sites. The Zero Saga is a good read for mathematicians, college and graduate level students in mathematics, or anyone interested in logic.
Christian Wiesendanger
2009-07-25
Isometrodynamics (ID), the gauge theory of the group of volume-preserving diffeomorphisms of an "inner" D-dimensional flat space, is tentatively interpreted as a fundamental theory of gravity. Dimensional analysis shows that the Planck length l_P - and through it \\hbar and \\Gamma - enters the gauge field action linking ID and gravity in a natural way. Noting that the ID gauge field couples solely through derivatives acting on "inner" space variables all ID fields are Taylor-expanded in "inner" space. Integrating out the "inner" space variables yields an effective field theory for the coefficient fields with l_P^2 emerging as the expansion parameter. For \\hbar goint to zero only the leading order field does not vanish. This classical field couples to the matter Noether currents and charges related to the translation invariance in "inner" space. A model coupling this leading order field to a matter point source is established and solved. Interpreting the matter Noether charge in terms of gravitational mass Newton's inverse square law is finally derived for a static gauge field source and a slowly moving test particle. Gravity emerges as potentially related to field variations over "inner" space and might microscopically be described by the ID gauge field or equivalently by an infinite string of coefficient fields only the leading term of which is related to the macroscopical effects of gravity.
NSDL National Science Digital Library
Twin Cities Public Television, Inc.
2007-01-01
This activity (located on page 3 of the PDF) is a full inquiry investigation into the forces of gravity and air pressure. Groups of learners will construct a simple gravity fountain by making a hole near the bottom of a 2-liter bottle, filling it with water, then as the bottle empties, collecting measurements of the water levels and length of the stream, to make a graph for analysis. Relates to linked video, DragonflyTV GPS: Gravity Fountain.
NASA Astrophysics Data System (ADS)
Magliaro, Elena; Perini, Claudio
2013-02-01
We consider spinfoam quantum gravity in the flipped limit, which is the double scaling limit ? ? 0, j ? ? with ?j = const., where ? is the Immirzi parameter, j is the spin and ?j gives the physical area in Planck units. In this regime the amplitude for a 2-complex becomes effectively an integral over Regge-like metrics and seems to enforce Einstein equations in the semiclassical regime. The Immirzi parameter must be considered as dynamical in the sense that it runs to zero when the fine structure of the foam is averaged. In addition to quantum corrections which vanish for ? ? 0, we find new corrections due to the discreteness of geometric spectra.
Zeroing in on supersymmetric radiation amplitude zeros
NASA Astrophysics Data System (ADS)
Hewett, Joanne L.; Ismail, Ahmed; Rizzo, Thomas G.
2011-12-01
Radiation amplitude zeros have long been used to test the standard model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the pT spectrum of the softest lepton in the trilepton ?1ą?20 decay channel to that of a control process such as ?1+?1- or ?20?20. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological minimal supersymmetric standard model, and find that it is effective in determining the wino content of the neutralino.
Ren-song Tsay
1991-01-01
An exact zero skew clock routing algorithm using the Elmore delay model is presented. Recursively in a bottom-up fashion, two zero-skewed subtrees are merged into a new tree with zero skew. The algorithm can be applied to single-staged clock trees, multi-staged clock trees, and multi-chip system clock trees. It is ideal for hierarchical methods of constructing large systems. All subsystems
Cynthia Dwork; Moni Naor; Amit Sahai
2004-01-01
Concurrent executions of a zero-knowledge protocol by a single prover (with one or more verifiers) may leak information and may not be zero-knowledge in toto. In this article, we study the problem of maintaining zero-knowledge.We introduce the notion of an (?, ?) timing constraint: for any two processors P1 and P2, if P1 measures ? elapsed time on its local
NASA Astrophysics Data System (ADS)
Ma?lanka, K.
A model of reality based on quantum fields, but with a classical treatment of gravity, is inconsistent. Finding a solution has proved extremely difficult, possibly due to the beauty and conceptual simplicity of general relativity. There is a variety of approaches to a consistent theory of quntum gravity. At present, it seems that superstring theory is the most promising candidate.
Healey, D.L. [Geological Survey, Denver, CO (USA)
1983-12-31
A large density contrast exists between the Paleozoic rocks (including the rocks of Climax stock) and less dense, Tertiary volcanic rocks and alluvium. This density contrast ranges widely, and herein for interpretive purposes, is assumed to average 0.85 Mg/m{sup 3} (megagrams per cubic meter). The large density contrast makes the gravity method a useful tool with which to study the interface between these rock types. However, little or no density contrast is discernible between the sedimentary Paleozoic rocks that surround the Climax stock and the intrusive rocks of the stock itself. Therefore the gravity method can not be used to define the configuration of the stock. Gravity highs coincide with outcrops of the dense Paleozoic rocks, and gravity lows overlie less-dense Tertiary volcanic rocks and Quaternary alluvium. The positions of three major faults (Boundary, Yucca, and Butte faults) are defined by steep gravity gradients. West of the Climax stock, the Tippinip fault has juxtaposed Paleozoic rocks of similar density, and consequently, has no expression in the gravity data in that area. The gravity station spacing, across Oak Spring Butte, is not sufficient to adequately define any gravity expression of the Tippinip fault. 18 refs., 5 figs.
Virtual waterless manufacturing: zero intake, zero emission.
Sharma, A
2003-01-01
Innovative application of a systematic approach to reduce freshwater intake and achieve zero emissions could help in reducing the adverse impact of industrial activity on world water resources. Cleantech is a strategic enviro-management technique to reduce the generation of pollutants in a process at source, through minor process modification, material substitution, improved manufacturing practices or low cost treatment. PMID:12731774
ERIC Educational Resources Information Center
Moore, Brian N.
2010-01-01
The concept of zero tolerance dates back to the mid-1990s when New Jersey was creating laws to address nuisance crimes in communities. The main goal of these neighborhood crime policies was to have zero tolerance for petty crime such as graffiti or littering so as to keep more serious crimes from occurring. Next came the war on drugs. In federal
ERIC Educational Resources Information Center
Wichowski, Chester
1979-01-01
The zero-based budgeting approach is designed to achieve the greatest benefit with the fewest undesirable consequences. Seven basic steps make up the zero-based decision-making process: (1) identifying program goals, (2) classifying goals, (3) identifying resources, (4) reviewing consequences, (5) developing decision packages, (6) implementing a
ERIC Educational Resources Information Center
Roland, Erling; Midthassel, Unni Vere
2012-01-01
Zero is a schoolwide antibullying program developed by the Centre for Behavioural Research at the University of Stavanger, Norway. It is based on three main principles: a zero vision of bullying, collective commitment among all employees at the school using the program, and continuing work. Based on these principles, the program aims to reduce
Einstein Gravity from Conformal Gravity
Juan Maldacena
2011-06-09
We show that that four dimensional conformal gravity plus a simple Neumann boundary condition can be used to get the semiclassical (or tree level) wavefunction of the universe of four dimensional asymptotically de-Sitter or Euclidean anti-de Sitter spacetimes. This simple Neumann boundary condition selects the Einstein solution out of the more numerous solutions of conformal gravity. It thus removes the ghosts of conformal gravity from this computation. In the case of a five dimensional pure gravity theory with a positive cosmological constant we show that the late time superhorizon tree level probability measure, $|\\Psi [ g ]|^2$, for its four dimensional spatial slices is given by the action of Euclidean four dimensional conformal gravity.
The Dark Gravity model predictions for Gravity Probe B
Frederic Henry-Couannier
2007-10-23
The previous version of this article gave erroneous predictions. The correct uptodate predictions can be found in the section devoted to gravitomagnetism in the living review of the Dark Gravity theory: gr-qc/0610079 The most natural prediction is zero frame dragging and the same geodetic effect as predicted by GR. However, a straightforward extension of the theory could lead to the same frame-dragging as in GR.
Zero-point length from string fluctuations
Michele Fontanini; Euro Spallucci; T. Padmanabhan
2005-09-15
One of the leading candidates for quantum gravity, viz. string theory, has the following features incorporated in it. (i) The full spacetime is higher dimensional, with (possibly) compact extra-dimensions; (ii) There is a natural minimal length below which the concept of continuum spacetime needs to be modified by some deeper concept. On the other hand, the existence of a minimal length (or zero-point length) in four-dimensional spacetime, with obvious implications as UV regulator, has been often conjectured as a natural aftermath of any correct quantum theory of gravity. We show that one can incorporate the apparently unrelated pieces of information - zero-point length, extra-dimensions, string T-duality - in a consistent framework. This is done in terms of a modified Kaluza-Klein theory that interpolates between (high-energy) string theory and (low-energy) quantum field theory. In this model, the zero-point length in four dimensions is a ``virtual memory'' of the length scale of compact extra-dimensions. Such a scale turns out to be determined by T-duality inherited from the underlying fundamental string theory. From a low energy perspective short distance infinities are cut off by a minimal length which is proportional to the square root of the string slope, i.e. \\sqrt{\\alpha^\\prime}. Thus, we bridge the gap between the string theory domain and the low energy arena of point-particle quantum field theory.
NASA Astrophysics Data System (ADS)
Soffel, M.
The present status of experimental gravity is reviewed. The author discusses experimental tests of Newton's law of gravity (the 1/r2-law, G?/G and the numerical value of G), of various forms of the equivalence principle (the weak equivalence principle, Einstein's equivalence principle and the strong equivalence principle related with the Nordtvedt effect) as well as various tests of metric theories of gravity. Among the latter he describes the search for gravito-magnetism (Lense-Thirring effects), measurements of the geodetic precession and light-deflection (signal retardation) effects. The important topics of binary pulsars and gravitational wave physics are beyond the scope of that article.
THE ZERO MODES AND ZERO RESONANCES OF MASSLESS DIRAC OPERATORS
THE ZERO MODES AND ZERO RESONANCES OF MASSLESS DIRAC OPERATORS YOSHIMI SAIT â?˘ O AND TOMIO UMEDA Abstract. The zero modes and zero resonances of the Dirac operator H = # Âˇ D+Q(x) are discussed, whereĂ?4 Hermitian matrixÂ valued function with |q jk (x)| # C#x# -# , # > 1. We shall show that every zero mode f
Lujan, Richard E. (Santa Fe, NM)
2001-01-01
A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.
NASA Astrophysics Data System (ADS)
Marcos, Joăo S.; Silveirinha, Mário G.; Engheta, Nader
2015-05-01
Here we theoretically predict and experimentally verify that permeability ľ-near-zero (MNZ) materials give the opportunity to supercouple waveguides with highly mismatched cross sections. Rather distinct from the supercoupling provided by permittivity-near-zero materials we discovered several years ago, the MNZ supercoupling can take place when the transition channel cross section is much wider than that of the input and output waveguides. We develop a simple analytical model that captures the physical mechanisms that enable this remarkable effect. The MNZ supercoupling effect is experimentally verified with rectangular waveguide technology by mimicking the ľ-near-zero response with the help of cylindrical split ring resonators.
M. Soffel
1998-01-01
The present status of experimental gravity is reviewed. The author discusses experimental tests of Newton's law of gravity (the 1\\/r2-law, G˙\\/G and the numerical value of G), of various forms of the equivalence principle (the weak equivalence principle, Einstein's equivalence principle and the strong equivalence principle related with the Nordtvedt effect) as well as various tests of metric theories of
ERIC Educational Resources Information Center
Fischer, William B.; Stauffer, Robert A.
1978-01-01
Erie County Community College (New York) has developed a zero-based program budgeting system to meet current fiscal problems and diminished resources. The system allocates resources on the basis of program effectiveness and market potential. (LH)
NSDL National Science Digital Library
Elliott Kimmel may have created zeroBio for the students of London, Ontario's Central Secondary School, but high school biology students anywhere would benefit tremendously from a visit to this extensive collection of biology learning resources. In addition to functioning as an online biology textbook, zeroBio offers dissection photos for a number of specimens, multimedia presentations, self-quizzing flashcards for organic chemistry, downloadable worksheets, interactive quizzes, games, puzzles, and more.
Development and Design of Zero-g Liquid Quantity Gauge for Solar Thermal Vehicle
Franklin T. Dodge; Steven T. Green; Steven P. Petullo; Neil T. VanDresar
2002-01-01
The development and design of a cryogenic liquid quantity gauge for zero-gravity (zero-g) applications are described. The gauge, named the compression mass gauge (CMG), operates on the principle of slightly changing the volume of the tank by an oscillating bellows. The resulting pressure change is measured and used to predict the volume of vapor in the tank, from which the
Electrodynamics of midlatitude spread F 2. A new theory of gravity wave electric fields
Clark A. Miller
1997-01-01
In this paper, we investigate the response of the nighttime, midlatitude ionosphere to atmospheric gravity waves in the presence of the global dynamo electric field. Previous theories of gravity wave-ionosphere interaction have neglected the zero-order electric field generated by the global dynamo. We find, however, that gravity wave winds carrying the ionosphere upward and downward along the tilted midlatitude magnetic
Drag phenomena from holographic massive gravity
Matteo Baggioli; Daniel K. Brattan
2015-04-28
We consider the motion of point particles in a strongly coupled field theory with broken translation invariance. We obtain the energy and momentum loss rates and drag coefficients for a class of such particles by solving for the motion of classical strings in holographic massive gravity. At low temperatures compared to the graviton mass the behaviour of the string is controlled by the appearance of an exotic ground state with non-zero entropy at zero temperature. Additionally we find an upper bound on the diffusion constant for a collection of these particles which is saturated when the mass of the graviton goes to zero.
Drag phenomena from holographic massive gravity
Baggioli, Matteo
2015-01-01
We consider the motion of point particles in a strongly coupled field theory with broken translation invariance. We obtain the energy and momentum loss rates and drag coefficients for a class of such particles by solving for the motion of classical strings in holographic massive gravity. At low temperatures compared to the graviton mass the behaviour of the string is controlled by the appearance of an exotic ground state with non-zero entropy at zero temperature. Additionally we find an upper bound on the diffusion constant for a collection of these particles which is saturated when the mass of the graviton goes to zero.
Water Immersion Reduced-Gravity Simulation
Otto F. Trout; William J. Bruchey
1969-01-01
A water immersion technique for simulating zero- and partial-gravity conditions has been developed and employed to examine several extravehicular task areas in space. The technique allows the pressure-suited subject to move in six degrees of freedom unencumbered by connecting supports and simulates his biomechanical performance in weightless space. The technique is useful in examining the astronaut's capability to execute extravehicular
Rex A. C. Medeiros; Francisco M. De Assis
2006-11-08
We define here a new kind of quantum channel capacity by extending the concept of zero-error capacity for a noisy quantum channel. The necessary requirement for which a quantum channel has zero-error capacity greater than zero is given. Finally, we point out some directions on how to calculate the zero-error capacity of such channels.
May, J. Peter
Measure Zero Henry Y. Chan July 1, 2013 1 Measure Zero Lebesgue measure gives a concrete way about sets which have Lebesgue measure zero. These sets are "small" in some senses, but they can behave is said to have measure zero if for every > 0, there exist open cubes U1, U2, Âˇ Âˇ Âˇ such that A i=1 Ui
Athanasios Markou
2009-03-03
Motivated mainly by the fact that no charged elementary particles having zero mass have been observed up to now, we investigate the question whether the mass of the elementary particles is connected with their electric charge and whether gravity can be derived from QED. The graviton is considered as a two-photon bound state. A relation between mass and charge of elementary particles is derived. Masses of the light quarks $d$ and $u$ are calculated from the electron mass, assuming that $d$, $u$ and $e$ are all fundamental and not composite. In this picture, the heavier quarks and leptons are considered as not fundamental, the massive neutral gauge bosons (and then their charged partners) are composite. The here calculated $u$ and $d$ quark masses, result in quark-mass ratios which display interesting regularities. The lightest quark mass turns out to be quite small. This may be interesting in connection to the strong CP problem.
ERIC Educational Resources Information Center
Pipinos, Savas
2010-01-01
This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity
NASA Astrophysics Data System (ADS)
Mukohyama, Shinji
2013-09-01
The concept of mass has been central in many areas of physics. Gravitation is not an exception, and it has been one of the long-standing questions whether the graviton, a spin-2 particle that mediates gravity, can have a non-vanishing mass or not. This question is relevant from not only theoretical but also phenomenological viewpoints, since a nonzero graviton mass may lead to late-time acceleration of the universe and thus may be considered as an alternative to dark energy. In 2010, de Rham, Gabadadze and Tolley proposed the first example of a fully nonlinear massive gravity theory and showed that the so called Boulware-Deser ghost, which had been one of the major obstacles against a stable nonlinear theory of massive gravity since 1972, can be removed by construction. Since then, nonlinear massive gravity has been attracting significant interest among physicists and cosmologists. The nonlinear theory of massive gravity provides a theoretical framework in which properties of the remaining five physical degrees of freedom of massive gravity can be studied. As always with any low-energy effective theories, one of the first tasks would be to identify good and bad backgrounds. Depending on the choice of backgrounds, some of the five degrees of freedom may become strongly coupled, may exhibit instantaneous propagation, or may lead to ghost/gradient instabilities. A related subject is to seek interesting solutions such as those relevant for astrophysical objects and those describing self-accelerating cosmology. Those solutions will allow us to study phenomenological and cosmological implications of the theory. Yet another important task would be to seek a possible (partial) UV completion that can be applied beyond the regime of validity of the low-energy effective theory that we currently know of. We invited articles to cover those important subjects in massive gravity. Given the recent rapid developments in the field, however, it must be noted that this focus issue should be best considered as a snapshot. We still hope that the collection of articles provides readers with guidance to the research at the frontier and ideally expedites further progress in the field. Shinji MukohyamaGuest Editor
Emergent gravity from a mass deformation in warped spacetime
Gherghetta, Tony; Peloso, Marco [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Poppitz, Erich [Department of Physics, University of Toronto, Toronto, ON M5S 1A7 (Canada)
2005-11-15
We consider a deformation of five-dimensional warped gravity with bulk and boundary mass terms to quadratic order in the action. We show that massless zero modes occur for special choices of the masses. The tensor zero mode is a smooth deformation of the Randall-Sundrum graviton wave function and can be localized anywhere in the bulk. There is also a vector zero mode with similar localization properties, which is decoupled from conserved sources at tree level. Interestingly, there are no scalar modes, and the model is ghost-free at the linearized level. When the tensor zero mode is localized near the IR brane, the dual interpretation is a composite graviton describing an emergent (induced) theory of gravity at the IR scale. In this case Newton's law of gravity changes to a new power law below the millimeter scale, with an exponent that can even be irrational.
Emergent Gravity from a Mass Deformation in Warped Spacetime
Gherghetta, Tony; Poppitz, E; Gherghetta, Tony; Peloso, Marco; Poppitz, Erich
2005-01-01
We consider a deformation of five-dimensional warped gravity with bulk and boundary mass terms to quadratic order in the action. We show that massless zero modes occur for special choices of the masses. The tensor zero mode is a smooth deformation of the Randall-Sundrum graviton wavefunction and can be localized anywhere in the bulk. There is also a vector zero mode with similar localization properties, which is decoupled from conserved sources at tree level. Interestingly, there are no scalar modes, and the model is ghost-free at the linearized level. When the tensor zero mode is localized near the IR brane, the dual interpretation is a composite graviton describing an emergent (induced) theory of gravity at the IR scale. In this case Newton's law of gravity changes to a new power law below the millimeter scale, with an exponent that can even be irrational.
ERIC Educational Resources Information Center
Techniques: Connecting Education and Careers, 2002
2002-01-01
Describes the robots used to aid in rescue and recovery at Ground Zero after the September 11, 2001 attack on the World Trade Center. The robots were developed as a result of national Science Foundation Quick Response Research Awards. Describes several awards that were made following the attack. (JOW)
Those Elusive Imaginary Zeros.
ERIC Educational Resources Information Center
Travers, Robert; Kim, David
1982-01-01
A method for finding the complex roots of a graph is detailed. A conjecture is made regarding the nature of zero points of fourth-degree polynomial functions, but it is not proven in general. Mathematical induction is viewed as a promising tool to prove the conjecture that turned out unproductive. (MP)
Gravity and positional homeostasis of the cell
NASA Astrophysics Data System (ADS)
Nace, George W.
Normally bilateralization takes place in the presence of the Earth's gravity which produces torque, shear, tension and compression acting upon the naked aggregates of cytoplasm in the zygote which is only stabilized by a weak cytoskeleton. In an initial examination of the effects of these quantities on development, an expression is derived to describe the tendency of torque to rotate the egg and reorganize its constituents. This expression yields the net torque resulting from buoyancy and gravity acting upon a dumbbell shaped cell with heavy and light masses at either end and ``floating'' in a medium. Using crude values for the variables, torques of 2.5 × 10-13 to 8.5 × 10-1 dyne-cm are found to act upon cells ranging from 6.4 ?m to 31 mm (chicken egg). By way of comparison six microtubules can exert a torque of 5 × 10-9 dyne-cm. (1) Gravity imparts torque to cells; (2) torque is reduced to zero as gravity approaches zero; and (3) torque is sensitive to cell size and particulate distribution. Cells must expend energy to maintain positional homeostasis against gravity. Although not previously recognized, Skylab 3 results support this hypothesis: tissue cultures used 58% more glucose on Earth than in space. The implications for developmental biology, physiology, genetics, and evolution are considered. At the cellular and tissue level the concept of ``gravity receptors'' may be unnecessary.
NSDL National Science Digital Library
Miss Rounds
2010-04-30
In this assignment you will learn all about gravity, and how it affects you. Today we are going to talk about Gravity. Let's see what Bill Nye the Science Guy says about gravity. Bill Nye and Gravity Bill Nye showed us what gravity is. but now we need to define it. What is gravity? Why do we need it? What would happen if there was no gravity? Go through each ...
Is nonrelativistic gravity possible?
Kocharyan, A. A. [School of Mathematical Sciences, Monash University, Clayton 3800 (Australia)
2009-07-15
We study nonrelativistic gravity using the Hamiltonian formalism. For the dynamics of general relativity (relativistic gravity) the formalism is well known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the lapse function is constrained correctly, then nonrelativistic gravity is described by a consistent Hamiltonian system. Surprisingly, nonrelativistic gravity can have solutions identical to relativistic gravity ones. In particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of Horava gravity are locally identical.
Static Spherically Symmetric Solution of (R +- ?^4/R) Gravity
Kh. Saaidi; A. Vaji; A. Aghamomammadi
2010-01-23
The static spherically symmetric solution for (R +- {\\mu}^4/R) model of f(R)gravity is investigated. We obtain the metric for space-time in the solar system that reduces to the Schwarzschild metric, when {\\mu} tends to zero. For the obtained metric, the deviation from Einstein gravity is very small. This result is different from the other results have been obtained by equivalence between f(R) gravity and scalar tensor theory. Also it is shown that the vacuum solution in the solar system depends on the shape of matter distribution which differ from the Einstein's gravity.
Separation Of Liquid And Gas In Zero Gravity
NASA Technical Reports Server (NTRS)
Howard, Frank S.; Fraser, Wilson S.
1991-01-01
Pair of reports describe scheme for separating liquid from gas so liquid could be pumped. Designed to operate in absence of gravitation. Jet of liquid, gas, or liquid/gas mixture fed circumferentially into cylindrical tank filled with liquid/gas mixture. Jet starts liquid swirling. Swirling motion centrifugally separates liquid from gas. Liquid then pumped from tank at point approximately diametrically opposite point of injection of jet. Vortex phase separator replaces such devices as bladders and screens. Requires no components inside tank. Pumps for gas and liquid outside tank and easily accessible for maintenance and repairs.
Dental equipment test during zero-gravity flight
NASA Technical Reports Server (NTRS)
Young, John; Gosbee, John; Billica, Roger
1991-01-01
The overall objectives of this program were to establish performance criteria and develop prototype equipment for use in the Health Maintenance Facility (HMF) in meeting the needs of dental emergencies during space missions. The primary efforts during this flight test were to test patient-operator relationships, patent (manikin) restraint and positioning, task lighting systems, use and operation of dental rotary instruments, suction and particle containment system, dental hand instrument delivery and control procedures, and the use of dental treatment materials. The initial efforts during the flight focused on verification of the efficiency of the particle containment system. An absorptive barrier was also tested in lieu of the suction collector. To test the instrument delivery system, teeth in the manikin were prepared with the dental drill to receive restorations, some with temporary filling materials and another with definitive filling material (composite resin). The best particle containment came from the combination use of the laminar-air/suction collector in concert with immediate area suction from a surgical high-volume suction tip. Lighting in the treatment area was provided by a flexible fiberoptic probe. This system is quite effective for small areas, but for general tasks ambient illumination is required. The instrument containment system (elastic cord network) was extremely effective and easy to use. The most serious problem with instrument delivey and actual treatment was lack of time during the microgravity sequences. The restorative materials handled and finished well.
Heat pipe zero gravity payload on ASTRO 8\\/II
P. H. Pawlowski; H. Koch; H. Kreeb
1979-01-01
The paper describes the details of a heat pipe experiment launched as a part payload onboard an Aries sounding rocket at White Sands Missile Range, Las Cruces, N. Mex., on June 12, 1978. Launcher data, preflight tests, experiment electronics and the flight results are described. The comparison between the flight simulation tests and the flight experiment data shows an excellent
Design, development, and operation of a zero gravity shower
NASA Technical Reports Server (NTRS)
Middleton, R. L.; Krupnick, A. C.; Reily, J. C.; Schrick, B. J.
1974-01-01
The high mission penalty associated with water and electrical power usage constrained the shower configuration concept for the Skylab project to a procedure in which water is sprayed on the body to wet down and soaping is accomplished without water flow. The soap is then finally rinsed off. Initial concept confirmation tests are discussed along with details of the flight shower configuration, the shower water bottle, the shower stall assembly, the liquid-gas separator, the collection box and bag assembly, the hydrophobic filter assembly, and the soap dispenser. Aspects of microbial evaluation of flight qualification hardware are also considered.
Bahram Mashhoon
2012-10-09
The analysis of measurements of accelerated observers in Minkowski spacetime has led to the development of nonlocal special relativity theory. Inertia and gravitation are intimately connected in accordance with the principle of equivalence. We therefore seek a nonlocal generalization of the theory of gravitation such that in the new theory the field equations are integro-differential equations for the local gravitational field. We show that it is possible to develop a nonlocal generalization of Einstein's theory of gravitation via the introduction of a scalar "constitutive" kernel in the teleparallel equivalent of general relativity. The resulting nonlocal theory is essentially equivalent to Einstein's theory plus "dark matter". That is, nonlocality simulates dark matter by introducing a new source term into general relativity. In the linear approximation for the nonlocal modification of Newtonian gravity, we recover the theoretical basis for the phenomenological Tohline-Kuhn modified gravity approach to the explanation of the astrophysical evidence for dark matter.
C. P. Kouropoulos
2002-11-14
I consider a pair of harmonic, electromagnetically coupled oscillators. Their dynamic coupling is allowed in the near field, that is, for frequencies roughly below ~c/r for virtual exchanges between two elementary entities. It is also valid for tunneling photons from very distant and red-shifted matter in the radiation gauge. In this case, the near magnetic field can be safely ignored. I treat the problem using Planck's and Post's ensemble description of harmonic oscillators. It is found that the correlated interacting modes have lower eigen frequencies and positive zero-modes, their anticorrelating counterparts having higher eigenfrequencies and negative zero-modes. While the former tend to induce coherent states over large ensembles, the latter cannot. This applies to all the modes of the near field, as well as to the transverse radiant modes. As a result, an attractive -1/r long-range potential is found in all the zero-modes of the near field, with a cosmological constant depending on the disorder in the system, provided that the interacting modes be most strongly cohered from the far infrared. This occurs naturally in Yilmaz's cosmology, where the Zitterbewegung of very distant matter is felt in the far infrared by the Zitterbewegung of local matter, in proportion to the frequencies of both, which agrees with the principle of equivalence. The Machian inertia appears on cosmic scales from bound coherent states through this tunneling electromagnetic radiation. In an elliptic Universe, the very low frequency modes of the coupled oscillators can be identified with those of their radiative antipodal image. As a result, far infrared coherent modes are expected to arise in the Universe that lies within their realm, in which the local oscillators intrinsically partake, inducing gravity.
Manuel Blum; Alfredo De Santis; Silvio Micali; Giuseppe Persiano
1991-01-01
We investigate the possibility of disposing of interaction between Prover and Verifier in a zeroknowledgeproof if they share beforehand a short random string.Without any assumption, we prove that non-interactive zero-knowledge proofs exist for some numbertheoretic languages for which no efficient algorithm is known.If deciding quadratic residuosity (modulo composite integers whose factorization is not known) iscomputationally hard, we show that the
Codimension zero superembeddings
J. M. Drummond; P. S. Howe
2001-05-31
Superembeddings which have bosonic codimension zero are studied in 3,4 and 6 dimensions. The worldvolume multiplets of these branes are off-shell vector multiplets in these dimensions, and their self-interactions include a Born-Infeld term. It is shown how they can be written in terms of standard vector multiplets in flat superspace by working in the static gauge. The action formula is used to determine both Green-Schwarz type actions and superfield actions.
NSDL National Science Digital Library
Mrs. Benson
2010-01-26
Learn more about gravity! 1 .So, what is gravity? What does it do? Why is it so important? Use your worksheet and fill write down the things it tells you about gravity. Gravity info 2. Now, let's go back to that same website and imagine what would happen if the force of gravity was turned off. ...
Inertial waste separation system for zero G WMS
NASA Technical Reports Server (NTRS)
1971-01-01
The design, operation, and flight test are presented for an inertial waste separation system. Training personnel to use this system under simulated conditions is also discussed. Conclusions indicate that before the system is usable in zero gravity environments, a mirror for the user's guidance should be installed, the bounce cycle and bag changing system should be redesigned, and flange clips should be added to improve the user's balance.
Graviresponses of osteocytes under altered gravity
NASA Astrophysics Data System (ADS)
Di, S. M.; Qian, A. R.; Qu, L. N.; Zhang, W.; Wang, Z.; Ding, C.; Li, Y. H.; Ren, H. G.; Shang, P.
2011-09-01
Single cell was capable of sensing and responding to alterations of gravity. Osteocytes, as the most abundant cells of the bone tissue playing an important role in the bone mechanotransduction, are very sensitive to mechanical stimuli. However, the effect of altered gravity on osteocytes so far is less known according to the public papers. Further study on this issue will help to verify and develop the theory of how cells perceive and respond to gravity. It also brings new ideas to the study of space bone loss. In our study, Osteocyte-like MLO-Y4 cells were exposed to 30 parabolic flights three times on ZERO-G airbus A300 to investigate the comprehensive effect on osteocytes stimulated by hyper- and hypo-gravity forces. It showed that the cell morphology, as well as cell area and height, was not changed significantly by hyper-gravity and hypo-gravity. However, the cytoskeleton was reorganized. In flight cells, F-actin polymerization was enhanced at the cell periphery and microtubule organizing center disappeared, but no apoptotic feathers were detected. The results of western blot showed that connexin 43 (Cx43) expression was down-regulated, indicating an decrease of gap-junction. In conclusion, hyper- and hypo-gravity stimulation altered the cytoskeleton architecture and suppressed gap-junction of osteocyte-like MLO-Y4 cells.
Jia, Yan-Bin
Recovering the Gravity-free Shape and Stiffness Matrix of a Deformable Solid for Accurate Modeling this matrix over the body's shape, neglecting the fact that it is already deformed under gravity of gravity on deformation, more prominent over a 3D solid, needs to resort to the stiffness matrix under zero
Zero Tolerance Policies. Research Brief
ERIC Educational Resources Information Center
Muir, Mike
2004-01-01
Much of this brief comes from the ERIC Digest on Zero Tolerance Policies (ERIC #: ED451579). State legislatures and school boards are adopting a growing number of zero-tolerance polices toward weapons, guns, and violence. Zero-tolerance polices are rules intended to address specific school-safety issues. Despite the controversies that it has
Precise Zero Knowledge Silvio Micali
Keinan, Alon
Precise Zero Knowledge Silvio Micali Rafael Pass December 1, 2007 Abstract We put forward the notion of Precise Zero Knowledge and provide its first implementations in a variety of settings under standard complexity assumptions. Whereas the classical notion of Zero Knowledge bounds the knowledge
Gravity and tectonic patterns of Mercury
NASA Astrophysics Data System (ADS)
Matsuyama, I.; Nimmo, F.
2008-12-01
We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinning, and reorientation on the global-scale gravity, shape, and tectonic patterns of planetary bodies. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J2/C22=10/3 and (b-c)/(a-c)=1/4, arise due to non-synchronous rotation and non-zero eccentricity even in the absence of reorientation or despinning. Reorientation or despinning induce additional variations. As an illustration of this theory, we consider the specific example of Mercury. The large gravity coefficients estimated from the Mariner 10 flybys cannot be attributed to the Caloris basin alone since the required mass excess in this case would have caused Caloris to migrate to one of Mercury's hot poles. Similarly, a large remnant bulge due to a smaller semimajor axis and spin-orbit resonance can be dismissed since the required semimajor axis is unphysically small (< 0.1 AU). Reorientation of a large remnant bulge recording an epoch of faster rotation (without significant semimajor axis variations) can explain the large gravity coefficients. This requires initial rotation rates > 20 times the present value and a positive gravity anomaly associated with Caloris capable of driving 10-45° equatorward reorientation. The required gravity anomaly can be explained by infilling of the basin with material of thicknesses > 7 km, or an annulus of volcanic plains emplaced around the basin with annulus width ~ 1200 km and fill thicknesses > 2 km. The predicted tectonic pattern due to these despinning and reorientation scenarios and radial contraction is in good agreement with the observed lobate scarp pattern.
NSDL National Science Digital Library
On a hot day, some might wish they could get the temperature down a bit. They might not wish it to be as cold as, say absolute zero, but there are many scientists who are interested in doing just that. For those who are curious, absolute zero clocks in at around minus 460 degrees Fahrenheit. This engaging website is meant to serve as a complementary resource to the two-part series that recently aired on NOVA on this engaging topic. Visitors can start by watching a short preview of the program, and then continuing on to look over some of the special interactive features on the site. All told, there are ten different features, including "A Sense of Scale", "How Low Can You Go?", and "Milestones in Cold Research". The "Milestones in Cold Research" is a great place to start, as it's an interactive timeline that chronicles the "netherworld of extraordinarily low temperatures" as investigated by everyone from Galileo to current researchers. Of course, there are also more playful features here, such as "The Ice Trade", which asks users to dispatch ships loaded with natural ice to Florida, Brazil, and India.
The zero point energy and gravitation
Hristu Culetu
2004-11-22
A possible connection between the energy W of the vacuum fluctuations of quantum fields and gravity in "empty space" is conjectured in this paper using a natural cutoff of high momenta with the help of the gravitational radius of the vacuum region considered. We found that below some "critical" length $L = 1 mm$ the pressure $sigma$ is one third of the energy density $epsilon$, as for dark matter, but above $1 mm$ the equation of state is $sigma = -(epsilon)$ (dark energy). In the case of a massive field, W does not depend on the mass of the field for $L>1 mm$ it does not depend on the Planck constant. In addition, when the Newton constant tends to zero, W becomes infinite. The energy density is also a function of the volume V of the vacuum region taken into account.
Survival of scalar zero modes in warped extra dimensions
George, Damien P. [Nikhef Theory Group, Science Park 105, 1098 XG Amsterdam (Netherlands)
2011-05-15
Models with an extra dimension generally contain background scalar fields in a nontrivial configuration, whose stability must be ensured. With gravity present, the extra dimension is warped by the scalars, and the spin-0 degrees of freedom in the metric mix with the scalar perturbations. Where possible, we formally solve the coupled Schroedinger equations for the zero modes of these spin-0 perturbations. When specializing to the case of two scalars with a potential generated by a superpotential, we are able to fully solve the system. We show how these zero modes can be used to construct a solution matrix, whose eigenvalues tell whether a normalizable zero mode exists, and how many negative mass modes exist. These facts are crucial in determining stability of the corresponding background configuration. We provide examples of the general analysis for domain-wall models of an infinite extra dimension and domain-wall soft-wall models. For five-dimensional models with two scalars constructed using a superpotential, we show that a normalizable zero mode survives, even in the presence of warped gravity. Such models, which are widely used in the literature, are therefore phenomenologically unacceptable.
NASA Astrophysics Data System (ADS)
Gach, J.-L.; Darson, D.; Guillaume, C.; Goillandeau, M.; Boissin, O.; Boulesteix, J.; Cavadore, C.
We present a completely new technique to readout CCDs, which can achieve much lower noise than classical techniques used since the 70's. This technique is based on digital analysis of the CCD's output signal instead of analog filtering coupled to an original filtering method. Despite several attempts carried out in the past to implement digital Correlated Double Sampling (CDS), this is the first time that a radical improvement in readout noise performance is shown. Developed with this noise level improvement in mind, the zero noise CCD concept is presented. This is highly interesting for low light level conditions, where the detector works in readout noise regime and not in photon noise regime. This is the case particularly when concerning carrying out medium to high resolution spectroscopy, or multiplex (scanning) observations.
Nash, Patrick Lee
2010-01-01
A theory of a new gravitational interaction is described. This theory follows naturally from a new Lagrangian formulation of Maxwell's theory for photons and electrons (and positrons) whose associated Euler Lagrange equations imply the conventional Maxwell equations, but which possesses new \\textbf{\\emph{bosonic}} spinor degrees of freedom that may be associated with a new type of fundamental gravitational interaction. The precise character of this gravitational interaction with a photon vector potential is explicitly defined in terms of a local U(1)-invariant Lagrangian in Eq.[\\ref{Lagrangian3}]. However in Section \\ref{ssec:Simple-Cosmolo-Model}, in order to parallel the well known Friedmann model in cosmology, a phenomenological description of the new gravitational interaction coupled to Newton-Einstein gravity that is sourced by an ideal fluid is discussed. % % To lay the foundation for a description of the new gravitational interaction our new formulation of Maxwell's theory must first be described. It i...
Rodriguez, Carlos
Date Lot # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen BilirubinŽ(Bilirubin): Lot # Protein (Sulfosalicylic Acid): Lot # Specific Gravity - Saline 0.85 Specific Gravity - H20 RBC AND DATA ENTRY FORMS #12;Date Lot # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone
Rodriguez, Carlos
Date Lot # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen BilirubinŽ(Bilirubin): Lot # Protein (Sulfosalicylic Acid): Lot # Specific Gravity - Saline 0.85 Specific Gravity - H20 # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen Bilirubin Blood / Hemoglobin HCG
Low Gravity venting of Refrigerant 11
NASA Technical Reports Server (NTRS)
Labus, T. L.; Aydelott, J. C.; Lacovic, R. F.
1972-01-01
An experimental investigation was conducted in a five-second zero gravity facility to examine the effects of venting initially saturated Refrigerant 11 from a cylindrical container (15-cm diameter) under reduced gravitational conditions. The system Bond numbers studied were 0 (weightlessness), 9 and 63; the liquid exhibited a nearly zero-degree contact angle on the container surface. During the venting process, both liquid-vapor interface and liquid bulk vaporization occurred. The temperature of the liquid in the immediate vicinity of the liquid-vapor interface was found to decrease during venting, while the liquid bulk temperature remained constant. Qualitative observations of the effects of system acceleration, vent rate, and vapor volume presented. Quantitative information concerning the ullage pressure decay during low gravity venting is also included.
Minimum length, extra dimensions, modified gravity and black hole remnants
Maziashvili, Michael, E-mail: maziashvili@gmail.com [Particle Physics and Cosmology Group, Ilia State University, 3/5 Cholokashvili Ave., Tbilisi 0162, Georgia (United States)
2013-03-01
We construct a Hilbert space representation of minimum-length deformed uncertainty relation in presence of extra dimensions. Following this construction, we study corrections to the gravitational potential (back reaction on gravity) with the use of correspondingly modified propagator in presence of two (spatial) extra dimensions. Interestingly enough, for r?0 the gravitational force approaches zero and the horizon for modified Schwarzschild-Tangherlini space-time disappears when the mass approaches quantum-gravity energy scale. This result points out to the existence of zero-temperature black hole remnants in ADD brane-world model.
On the structure of the topological phase of two-dimensional gravity
Edward Witten
1990-01-01
The topological phase of two-dimensional gravity is re-examined. The correlation functions of the naturally occuring operators in the minimal topological model are computed, using topological methods, in genus zero and genus one. The genus-zero results agree with recent results obtained in exact solutions of ``matrix models'', suggesting that the two approaches to two-dimensional gravity are equivalent. The coupling of two-dimensional
Critical regimes of internal gravity wave generation
Vitaly V. Bulatov; Yuriy V. Vladimirov; Vasily A. Vakorin
2005-11-27
The problem of constructing an asymptotic representation of the solution of the internal gravity wave field exited by a source moving at a velocity close to the maximum group velocity of the individual wave mode is considered. For the critical regimes of individual mode generation the asymptotic representation of the solution obtained is expressed in terms of a zero-order Macdonald function. The results of numerical calculations based on the exact and asymptotic formulas are given.
The Dilemma of Zero Tolerance.
ERIC Educational Resources Information Center
Holloway, John H.
2002-01-01
Reviews research on the impact of zero-tolerance policies on student behavior and achievement. Concludes that policies are generally ineffective and often counterproductive. (Contains 14 references.) (PKP)
Dusty plasma cross-field instability excited by gravity
N. D'Angelo
2003-01-01
A cross-field instability is considered in a magnetized, dusty plasma acted upon by a gravity field, g, perpendicular to the magnetic field, B, permeating the plasma. Waves are produced traveling essentially with the dust grains zero-order motion. The condition for excitation of the instability is that the dust zero-order velocity perpendicular to both g and B exceed the dust-acoustic speed,
Locally Localized Gravity and Geometric Transitions
D. Bazeia; F. A. Brito; A. R. Gomes
2004-12-16
In this paper we analyze the local localization of gravity in $AdS_4$ thick brane embedded in $AdS_5$ space. The 3-brane is modelled by domain wall solution of a theory with a bulk scalar field coupled to five-dimensional gravity. In addition to small four-dimensional cosmological constant, the vacuum expectation value (vev) of the scalar field controls the emergence of a localized four-dimensional quasi-zero mode. We introduce high temperature effects, and we show that gravity localization on a thick 3-brane is favored below a critical temperature $T_c$. These investigations suggest the appearance of another critical temperature $T_*,$ where the thick 3-brane engenders the geometric $AdS/M/dS$ transitions.
Entropic force, noncommutative gravity, and ungravity
Nicolini, Piero [Frankfurt Institute for Advanced Studies (FIAS), Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main (Germany)
2010-08-15
After recalling the basic concepts of gravity as an emergent phenomenon, we analyze the recent derivation of Newton's law in terms of entropic force proposed by Verlinde. By reviewing some points of the procedure, we extend it to the case of a generic quantum gravity entropic correction to get compelling deviations to the Newton's law. More specifically, we study: (1) noncommutative geometry deviations and (2) ungraviton corrections. As a special result in the noncommutative case, we find that the noncommutative character of the manifold would be equivalent to the temperature of a thermodynamic system. Therefore, in analogy to the zero temperature configuration, the description of spacetime in terms of a differential manifold could be obtained only asymptotically. Finally, we extend the Verlinde's derivation to a general case, which includes all possible effects, noncommutativity, ungravity, asymptotically safe gravity, electrostatic energy, and extra dimensions, showing that the procedure is solid versus such modifications.
Observational Bounds on Modified Gravity Models
Antonio De Felice; Pia Mukherjee; Yun Wang
2007-06-08
Modified gravity provides a possible explanation for the currently observed cosmic accelaration. In this paper, we study general classes of modified gravity models. The Einstein-Hilbert action is modified by using general functions of the Ricci and the Gauss-Bonnet scalars, both in the metric and in the Palatini formalisms. We do not use an explicit form for the functions, but a general form with a valid Taylor expansion up to second order about redshift zero in the Riemann-scalars. The coefficients of this expansion are then reconstructed via the cosmic expansion history measured using current cosmological observations. These are the quantities of interest for theoretical considerations relating to ghosts and instabilities. We find that current data provide interesting constraints on the coefficients. The next-generation dark energy surveys should shrink the allowed parameter space for modifed gravity models quite dramatically.
Gravity-induced stresses in finite slopes
Savage, W.Z.
1994-01-01
An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.
Ziock, H.; Lackner, K.
2000-08-01
We discuss a novel, emission-free process for producing hydrogen or electricity from coal. Even though we focus on coal, the basic design is compatible with any carbonaceous fuel. The process uses cyclical carbonation of calcium oxide to promote the production of hydrogen from carbon and water. The carbonation of the calcium oxide removes carbon dioxide from the reaction products and provides the additional energy necessary to complete hydrogen production without additional combustion of carbon. The calcination of the resulting calcium carbonate is accomplished using the high temperature waste heat from solid oxide fuel cells (SOFC), which generate electricity from hydrogen fuel. Converting waste heat back to useful chemical energy allows the process to achieve very high conversion efficiency from fuel energy to electrical energy. As the process is essentially closed-loop, the process is able to achieve zero emissions if the concentrated exhaust stream of CO{sub 2} is sequestered. Carbon dioxide disposal is accomplished by the production of magnesium carbonate from ultramafic rock. The end products of the sequestration process are stable naturally occurring minerals. Sufficient rich ultramafic deposits exist to easily handle all the world's coal.
Multiphase Flow: The Gravity of the Situation
NASA Technical Reports Server (NTRS)
Hewitt, Geoffrey F.
1996-01-01
A brief survey is presented of flow patterns in two-phase, gas-liquid flows at normal and microgravity, the differences between them being explored. It seems that the flow patterns in zero gravity are in general much simpler than those in normal gravity with only three main regimes (namely bubbly, slug and annular flows) being observed. Each of these three regimes is then reviewed, with particular reference to identification of areas of study where investigation of flows at microgravity might not only be interesting in themselves, but also throw light on mechanisms at normal earth gravity. In bubbly flow, the main area of interest seems to be that of bubble coalescence. In slug flow, the extension of simple displacement experiments to the zero gravity case would appear to be a useful option, supplemented by computational fluid dynamics (CFD) studies. For annular flow, the most interesting area appears to be the study of the mechanisms of disturbance waves; it should be possible to extend the region of investigation of the onset and behavior of these waves to much low gas velocities where measurements are clearly much easier.
The mass, gravity field, and ephemeris of Mercury
NASA Technical Reports Server (NTRS)
Anderson, John D.; Esposito, Pasquale B.; Lau, Eunice L.; Trager, Gayle B.; Colombo, Giuseppe
1987-01-01
In the present gravity analysis of Mariner 10/Deep Space Network radio Doppler and range data for Mercury encounters in March 1974 and March 1975, a combined least-squares fit to the Doppler data has determined two second-degree gravity harmonics that are referred to a 2439-km equatorial radius. It is noted that the 1-sigma error limits on the gravity results encompass the possibility that harmonics other than J2 and C22 significantly differ from zero. The Deep Space Network radio range data obtained with Mariner 10 are primarily applicable to such improvements of Mercury's ephemeris as the more precise determination of perihelion precession.
Palatini formulation of modified gravity with squared scalar curvature
Xinhe Meng; Peng Wang
2004-08-29
In this paper we derive the Modified Friedmann equation in the Palatini formulation of $R^2$ gravity. Then we use it to discuss the problem of whether in Palatini formulation a $R^2$ term can drive an inflation. We show that the Palatini formulation of $R^2$ gravity cannot lead to gravity-driven inflation. If considering no zero radiation and matter energy densities, we show that only under rather restrictive assumption about the radiation and matter energy densities there will be a mild power-law inflation $a\\sim t^2$.
Aerosol bolus dispersion in acinar airwaysinfluence of gravity and airway asymmetry
Ma, Baoshun
2012-01-01
The aerosol bolus technique can be used to estimate the degree of convective mixing in the lung; however, contributions of different lung compartments to measured dispersion cannot be differentiated unambiguously. To estimate dispersion in the distal lung, we studied the effect of gravity and airway asymmetry on the dispersion of 1 ?m-diameter particle boluses in three-dimensional computational models of the lung periphery, ranging from a single alveolar sac to four-generation (g4) structures of bifurcating airways that deformed homogeneously during breathing. Boluses were introduced at the beginning of a 2-s inhalation, immediately followed by a 3-s exhalation. Dispersion was estimated by the half-width of the exhaled bolus. Dispersion was significantly affected by the spatial orientation of the models in normal gravity and was less in zero gravity than in normal gravity. Dispersion was strongly correlated with model volume in both normal and zero gravity. Predicted pulmonary dispersion based on a symmetric g4 acinar model was 391 ml and 238 ml under normal and zero gravity, respectively. These results accounted for a significant amount of dispersion measured experimentally. In zero gravity, predicted dispersion in a highly asymmetric model accounted for ?20% of that obtained in a symmetric model with comparable volume and number of alveolated branches, whereas normal gravity dispersions were comparable in both models. These results suggest that gravitational sedimentation and not geometrical asymmetry is the dominant factor in aerosol dispersion in the lung periphery. PMID:22678957
Stone, W.J.
1983-10-31
A zero-home locator includes a fixed phototransistor switch and a moveable actuator including two symmetrical, opposed wedges, each wedge defining a point at which switching occurs. The zero-home location is the average of the positions of the points defined by the wedges.
Ting-Hai Chao; J.-M. Ho; Y.-C. Hsu
1992-01-01
The authors present an algorithm, called the zero skew segment tree method (ZSTM), for the clock net routing problem. To eliminate the lock skew and minimize the total wire length, ZSTM recursively partitions the sink nodes into two subsets which have equal loadings and minimum sum of diameters, and then constructs a zero skew segment tree according to the partitioning
Scaling Theorems for Zero Crossings
Alan L. Yuille; Tomaso A. Poggio
1986-01-01
We characterize some properties of the zero crossings of the Laplacian of signalsżin particular imagesżfiltered with linear filters, as a function of the scale of the filter (extending recent work by Witkin [16]). We prove that in any dimension the only filter that does not create generic zero crossings as the scale increases is the Gaussian. This result can be
Zero knowledge proofs of identity
U. Fiege; Amos Fiat; Adi Shamir
1987-01-01
In this paper we extend the notion of zero knowledge proofs of membership (which reveal one bit of information) to zero knowledge proofs of knowledge (which reveal no information whatsoever). After formally defining this notion, we show its relevance to identification schemes, in which parties prove their identity by demonstrating their knowledge rather than by proving the validity of assertions.
Conformal symmetry of gravity and the cosmological constant problem
Cadoni, M
2006-01-01
In absence of matter Einstein gravity with a cosmological constant $\\Lambda$ can be formulated as a scale-free theory depending only on the dimensionless coupling constant $G \\Lambda$, where $G$ is Newton constant. In regimes where only the dynamics of the conformal factor of the metric is relevant, Einstein gravity can be described by a conformal field theory in four dimensions. In the cosmological framework the model describes the usual Friedmann-Robertson-Walker flat universe. The conformal symmetry of the gravity sector is broken by coupling with matter. The dimensional coupling constants $G$ and $\\Lambda$ are introduced by different terms in this coupling. If the vacuum of quantum matter fields respects the symmetry of the gravity sector, the vacuum energy has to be zero and the ``physical'' cosmological constant is generated by the coupling of gravity with matter. This could explain the tiny value of the observed energy density driving the accelerating expansion of the universe.
Chiral Gravity, Log Gravity and Extremal CFT
Alexander Maloney; Wei Song; Andrew Strominger
2009-03-26
We show that the linearization of all exact solutions of classical chiral gravity around the AdS3 vacuum have positive energy. Non-chiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity-- the theory with logarithmically relaxed boundary conditions --has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic CFT. Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We normally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.
Chiral gravity, log gravity, and extremal CFT
Maloney, Alexander [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Song Wei [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190 (China); Center for the Fundamental Laws of Nature Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States); Strominger, Andrew [Center for the Fundamental Laws of Nature Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States)
2010-03-15
We show that the linearization of all exact solutions of classical chiral gravity around the AdS{sub 3} vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.
Non-Newtonian gravity or gravity anomalies?
NASA Technical Reports Server (NTRS)
Rubincam, David P.; Chao, B. Fong; Schatten, Kenneth H.; Sager, William W.
1988-01-01
Geophysical measurements of G differ from laboratory values, indicating that gravity may be non-Newtonian. A spherical harmonic formulation is presented for the variation of (Newtonian) gravity inside the Earth. Using the GEM-10B Earth Gravitational Field Model, it is shown that long-wavelength gravity anomalies, if not corrected, may masquerade as non-Newtonian gravity by providing significant influences on experimental observation of delta g/delta r and G. An apparent contradiction in other studies is also resolved: i.e., local densities appear in equations when average densities of layers seem to be called for.
NASA Technical Reports Server (NTRS)
Page, L. W.; From, T. P.
1977-01-01
The behavior of liquids in zero gravity environments is discussed with emphasis on foams, wetting, and wicks. A multipurpose electric furnace (MA-010) for the high temperature processing of metals and salts in zero-g is described. Experiments discussed include: monolectic and synthetic alloys (MA-041); multiple material melting point (MA-150); zero-g processing of metals (MA-070); surface tension induced convection (MA-041); halide eutectic growth; interface markings in crystals (MA-060); crystal growth from the vapor phase (MA-085); and photography of crystal growth (MA-028).
Feeling Gravity's Pull: Gravity Modeling. The Gravity Field of Mars
NASA Technical Reports Server (NTRS)
Lemoine, Frank; Smith, David; Rowlands, David; Zuber, Maria; Neumann, G.; Chinn, Douglas; Pavlis, D.
2000-01-01
Most people take the constant presence of gravitys pull for granted. However, the Earth's gravitational strength actually varies from location to location. This variation occurs because mass, which influences an object's gravitational pull, is not evenly distributed within the planet. Changes in topography, such as glacial movement, an earthquake, or a rise in the ocean level, can subtly affect the gravity field. An accurate measurement of the Earth's gravity field helps us understand the distribution of mass beneath the surface. This insight can assist us in locating petroleum, mineral deposits, ground water, and other valuable substances. Gravity mapping can also help notice or verify changes in sea surface height and other ocean characteristics. Such changes may indicate climate change from polar ice melting and other phenomena. In addition, gravity mapping can indicate how land moves under the surface after earthquakes and other plate tectonic processes. Finally, changes in the Earth's gravity field might indicate a shift in water distribution that could affect agriculture, water supplies for population centers, and long-term weather prediction. Scientists can map out the Earth's gravity field by watching satellite orbits. When a satellite shifts in vertical position, it might be passing over an area where gravity changes in strength. Gravity is only one factor that may shape a satellite's orbital path. To derive a gravity measurement from satellite movement, scientists must remove other factors that might affect a satellite's position: 1. Drag from atmospheric friction. 2. Pressure from solar radiation as it heads toward Earth and. as it is reflected off the surface of the Earth 3. Gravitational pull from the Sun, the Moon, and other planets in the Solar System. 4. The effect of tides. 5. Relativistic effects. Scientists must also correct for the satellite tracking process. For example, the tracking signal must be corrected for refraction through the atmosphere of the Earth. Supercomputers can calculate the effect of gravity for specific locations in space following a mathematical process known as spherical harmonics, which quantifies the gravity field of a planetary body. The process is based on Laplace's fundamental differential equation of gravity. The accuracy of a spherical harmonic solution is rated by its degree and order. Minute variations in gravity are measured against the geoid, a surface of constant gravity acceleration at mean sea level. The geoid reference gravity model strength includes the central body gravitational attraction (9.8 m/sq s) and a geopotential variation in latitude partially caused by the rotation of the Earth. The rotational effect modifies the shape of the geoid to be more like an ellipsoid, rather than a perfect, circle. Variations of gravity strength from the ellipsoidal reference model are measured in units called milli-Galileos (mGals). One mGal equals 10(exp -5) m/sq s. Research projects have also measured the gravity fields of other planetary bodies, as noted in the user profile that follows. From this information, we may make inferences about our own planet's internal structure and evolution. Moreover, mapping the gravity fields of other planets can help scientists plot the most fuel-efficient course for spacecraft expeditions to those planets.
NUT-Charged Black Holes in Gauss-Bonnet Gravity
M. H. Dehghani; R. B. Mann
2005-11-30
We investigate the existence of Taub-NUT/bolt solutions in Gauss-Bonnet gravity and obtain the general form of these solutions in $d$ dimensions. We find that for all non-extremal NUT solutions of Einstein gravity having no curvature singularity at $r=N$, there exist NUT solutions in Gauss-Bonnet gravity that contain these solutions in the limit that the Gauss-Bonnet parameter $\\alpha$ goes to zero. Furthermore there are no NUT solutions in Gauss-Bonnet gravity that yield non-extremal NUT solutions to Einstein gravity having a curvature singularity at $r=N$ in the limit $% \\alpha \\to 0$. Indeed, we have non-extreme NUT solutions in $2+2k$ dimensions with non-trivial fibration only when the $2k$-dimensional base space is chosen to be $\\mathbb{CP}^{2k}$. We also find that the Gauss-Bonnet gravity has extremal NUT solutions whenever the base space is a product of 2-torii with at most a 2-dimensional factor space of positive curvature. Indeed, when the base space has at most one positively curved two dimensional space as one of its factor spaces, then Gauss-Bonnet gravity admits extreme NUT solutions, even though there a curvature singularity exists at $r=N$. We also find that one can have bolt solutions in Gauss-Bonnet gravity with any base space with factor spaces of zero or positive constant curvature. The only case for which one does not have bolt solutions is in the absence of a cosmological term with zero curvature base space.
NUT-charged black holes in Gauss-Bonnet gravity
Dehghani, M.H. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Department of Physics, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, 35 Caroline Street North, Waterloo, Ontario (Canada); Mann, R.B. [Department of Physics, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, 35 Caroline Street North, Waterloo, Ontario (Canada)
2005-12-15
We investigate the existence of Taub-NUT (Newman-Unti-Tamburino) and Taub-bolt solutions in Gauss-Bonnet gravity and obtain the general form of these solutions in d dimensions. We find that for all nonextremal NUT solutions of Einstein gravity having no curvature singularity at r=N, there exist NUT solutions in Gauss-Bonnet gravity that contain these solutions in the limit that the Gauss-Bonnet parameter {alpha} goes to zero. Furthermore there are no NUT solutions in Gauss-Bonnet gravity that yield nonextremal NUT solutions to Einstein gravity having a curvature singularity at r=N in the limit {alpha}{yields}0. Indeed, we have nonextreme NUT solutions in 2+2k dimensions with nontrivial fibration only when the 2k-dimensional base space is chosen to be CP{sup 2k}. We also find that the Gauss-Bonnet gravity has extremal NUT solutions whenever the base space is a product of 2-torii with at most a two-dimensional factor space of positive curvature. Indeed, when the base space has at most one positively curved two-dimensional space as one of its factor spaces, then Gauss-Bonnet gravity admits extreme NUT solutions, even though there a curvature singularity exists at r=N. We also find that one can have bolt solutions in Gauss-Bonnet gravity with any base space with factor spaces of zero or positive constant curvature. The only case for which one does not have bolt solutions is in the absence of a cosmological term with zero curvature base space.
Zero/zero rotorcraft certification issues. Volume 1: Executive summary
NASA Technical Reports Server (NTRS)
Adams, Richard J.
1988-01-01
This report analyzes the Zero/Zero Rotorcraft Certification Issues from the perspectives of manufacturers, operators, researchers and the FAA. The basic premise behind this analysis is the zero/zero, or at least extremely low visibility, rotorcraft operations are feasible today from both a technological and an operational standpoint. The questions and issues that need to be resolved are: What certification requirements do we need to ensure safety. Can we develop procedures which capitalize on the performance and maneuvering capabilities unique to rotorcraft. Will exptremely low visibility operations be economically feasible. This is Volume 1 of three. It provides an overview of the Certification Issues Forum held in Phoenix, Arizona in August of 1987. It presents a consensus of 48 experts from government, manufacturer, and research communities on 50 specific Certification Issues. The topics of Operational Requirements, Procedures, Airworthiness, and Engineering Capabilities are discussed.
Tethered gravity laboratories study
NASA Technical Reports Server (NTRS)
Lucchetti, F.
1989-01-01
Tethered gravity laboratories study is presented. The following subject areas are covered: variable gravity laboratory; attitude tether stabilizer; configuration analysis (AIT); dynamic analysis (SAO); and work planned for the next reporting period.
Towards noncommutative gravity
D. V. Vassilevich
2009-02-17
In this short article accessible for non-experts I discuss possible ways of constructing a non-commutative gravity paying special attention to possibilities of realizing the full diffeomorphism symmetry and to relations with 2D gravities.
Urine specific gravity is a laboratory test that shows the concentration of all chemical particles in the urine. ... changes to will tell the provider the specific gravity of your urine. The dipstick test gives only ...
Measurement of absolute gravity acceleration in Firenze
NASA Astrophysics Data System (ADS)
de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.
2011-01-01
This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ą 4.0) ?Gal and (980 492 048.3 ą 3.0) ?Gal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.
Terrestrial Gravity Fluctuations
Harms, Jan
2015-01-01
The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.
Terrestrial Gravity Fluctuations
Jan Harms
2015-07-21
The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.
Karim Noui
2010-03-31
We tackle the question of motion in Quantum Gravity: what does motion mean at the Planck scale? Although we are still far from a complete answer we consider here a toy model in which the problem can be formulated and resolved precisely. The setting of the toy model is three dimensional Euclidean gravity. Before studying the model in detail, we argue that Loop Quantum Gravity may provide a very useful approach when discussing the question of motion in Quantum Gravity.
BF Models in Dual Formulations of Linearized Gravity
Bizdadea, Constantin; Cioroianu, Eugen M.; Danehkar, Ashbiz; Iordache, Marius; Saliu, Solange O.; Sararu, Silviu C. [Faculty of Physics, University of Craiova, 13 A. I. Cuza Str., Craiova 200585 (Romania)
2009-05-22
The case of couplings in D = 5 between a simple, maximal BF model and the dual formulation of linearized gravity is considered. All the possible interactions are exhausted by means of computing the 'free' local BRST cohomology in ghost number zero.
Canadian low-gravity research using parabolic aircraft
Glen S. Campbell; L. Vezina; J. F. Aitken
1992-01-01
An active experimental program being implemented by Canada in microgravity, which relies heavily on the use of parabolic aircraft, is discussed. The advantages of zero-gravity aircraft include low cost and quick turnaround. These aircraft have demonstrated their value for prototyping experimental hardware developments planned for flight at other facilities, such as sounding rockets and Shuttle-based carriers which are supported by
Instanton representation of Plebanski gravity. Euclidean signature minisuperspace solution
Eyo Eyo Ita III
2012-06-11
Using the action for the instanton representation of Plebanski gravity (IRPG), we construct minisuperspace solutions restricted to diagonal variables. We have treated the Euclidean signature case with zero cosmological constant, depicting a gravitational analogy to free particle motion. This paper provides a testing ground for the IRPG for a simple case, which will be extended to the full theory in future work.
Zero-Energy COURTESY OF WAUSAU HOMES
Oak Ridge National Laboratory
Zero-Energy Homes COURTESY OF WAUSAU HOMES A SYSTEM BUILT WAUSAU HOME #12;Zero energy home features to being a zero energy home. Through its energy rightÂŽ program, TVA helps consumers adapt many-efficiency features are incorporated into zero-energy homes. Zero-energy homes are structures built with the eventual
ERIC Educational Resources Information Center
MacKeown, P. K.
1984-01-01
Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)
Stephen Hawking Quantum Gravity
Visser, Matt
Stephen Hawking and Quantum Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 4 Nov 2000 #12; Stephen Hawking and Quantum Gravity Abstract: Through research, Stephen Hawking has captured a place in the popular imagina- tion. Quantum gravity in its various
Quantum Physics Einstein's Gravity
Visser, Matt
Quantum Physics confronts Einstein's Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 13 October 2001 #12; Quantum Physics confronts Einstein's Gravity and with Einstein's theory of gravity (the general relativity) is still the single biggest theoretical problem
George Rupp; Frieder Kleefeld; Eef van Beveren
2004-12-06
A simple unitarized quark-meson model, recently applied with success to light and charmed scalar mesons, is shown to encompass Adler-type zeros in the amplitude, due to the use of relativistic kinematics in the scattering sector. These zeros turn out to be crucial for the description of the $K_0^*$(800) resonance, as well as the new charmed scalar mesons $D_{s0}^*$(2317) and $D_0^*$(2300). ~
Holographic Superconductor/Insulator Transition at Zero Temperature
Tatsuma Nishioka; Shinsei Ryu; Tadashi Takayanagi
2010-01-20
We analyze the five-dimensional AdS gravity coupled to a gauge field and a charged scalar field. Under a Scherk-Schwarz compactification, we show that the system undergoes a superconductor/insulator transition at zero temperature in 2+1 dimensions as we change the chemical potential. By taking into account a confinement/deconfinement transition, the phase diagram turns out to have a rich structure. We will observe that it has a similarity with the RVB (resonating valence bond) approach to high-Tc superconductors via an emergent gauge symmetry.
Grasping objects autonomously in simulated KC-135 zero-g
NASA Technical Reports Server (NTRS)
Norsworthy, Robert S.
1994-01-01
The KC-135 aircraft was chosen for simulated zero gravity testing of the Extravehicular Activity Helper/retriever (EVAHR). A software simulation of the EVAHR hardware, KC-135 flight dynamics, collision detection and grasp inpact dynamics has been developed to integrate and test the EVAHR software prior to flight testing on the KC-135. The EVAHR software will perform target pose estimation, tracking, and motion estimation for rigid, freely rotating, polyhedral objects. Manipulator grasp planning and trajectory control software has also been developed to grasp targets while avoiding collisions.
NSDL National Science Digital Library
Ms. Pace
2009-11-09
3rd grade new unit on gravity National Standard: Standard 4, objective 1. Objective: Students will understand that objects near the earth are pulled towards the earth by gravity. Demonstrate that gravity is a force. Does anyone know what is going to happen if I let go of this ball? Why do you think that will happen? Today we are going to answer these questions by talking about gravity! I want you to go to this website and take notes while you read about gravity. ology click on "meet ...
(abstract) Venus Gravity Field
NASA Technical Reports Server (NTRS)
Konopliv, A. S.; Sjogren, W. L.
1995-01-01
A global gravity field model of Venus to degree and order 75 (5772 spherical harmonic coefficients) has been estimated from Doppler radio tracking of the orbiting spacecraft Pioneer Venus Orbiter (1979-1992) and Magellan (1990-1994). After the successful aerobraking of Magellan, a near circular polar orbit was attained and relatively uniform gravity field resolution (approximately 200 km) was obtained with formal uncertainties of a few milligals. Detailed gravity for several highland features are displayed as gravity contours overlaying colored topography. The positive correlation of typography with gravity is very high being unlike that of the Earth, Moon, and Mars. The amplitudes are Earth-like, but have significantly different gravity-topography ratios for different features. Global gravity, geoid, and isostatic anomaly maps as well as the admittance function are displayed.
Quantization of Emergent Gravity
Hyun Seok Yang
2014-12-24
Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC spacetime, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing spacetime itself, leading to a dynamical NC spacetime. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.
A research of 3D gravity inversion based on the recovery of sparse underdetermined linear equations
NASA Astrophysics Data System (ADS)
Zhaohai, M.
2014-12-01
Because of the properties of gravity data, it is made difficult to solve the problem of multiple solutions. There are two main types of 3D gravity inversion methods?One of two methods is based on the improvement of the instability of the sensitive matrix, solving the problem of multiple solutions and instability in 3D gravity inversion. Another is to join weight function into the 3D gravity inversion iteration. Through constant iteration, it can renewal density values and weight function to achieve the purpose to solve the multiple solutions and instability of the 3D gravity data inversion. Thanks to the sparse nature of the solutions of 3D gravity data inversions, we can transform it into a sparse equation. Then, through solving the sparse equations, we can get perfect 3D gravity inversion results. The main principle is based on zero norm of sparse matrix solution of the equation. Zero norm is mainly to solve the nonzero solution of the sparse matrix. However, the method of this article adopted is same as the principle of zero norm. But the method is the opposite of zero norm to obtain zero value solution. Through the form of a Gaussian fitting solution of the zero norm, we can find the solution by using regularization principle. Moreover, this method has been proved that it had a certain resistance to random noise in the mathematics, and it was more suitable than zero norm for the solution of the geophysical data. 3D gravity which is adopted in this article can well identify abnormal body density distribution characteristics, and it can also recognize the space position of abnormal distribution very well. We can take advantage of the density of the upper and lower limit penalty function to make each rectangular residual density within a reasonable range. Finally, this 3D gravity inversion is applied to a variety of combination model test, such as a single straight three-dimensional model, the adjacent straight three-dimensional model and Y three-dimensional model. They are classical model. We find that the inversion results are basically consistent with the results of forward models. Finally we apply the 3D gravity inversion method to the actual gravity data in Texas of the USA state. And we get the 3D gravity inversion which is almost the same with previous results.
Riemann zeta zeros and zero-point energy
J. G. Dueńas; N. F. Svaiter
2013-11-26
We postulate the existence of a self-adjoint operator associated to a system with countably infinite number of degrees of freedom whose spectrum is the sequence of the nontrivial zeros of the Riemann zeta function. We assume that it describes a massive scalar field coupled to a background field in a $(d+1)$-dimensional flat space-time. The scalar field is confined to the interval $[0,a]$ in one dimension and is not restricted in the other dimensions. The renormalized zero-point energy of this system is presented using techniques of dimensional and analytic regularization. In even dimensional space-time, the series that defines the regularized vacuum energy is finite. For the odd-dimensional case, to obtain a finite vacuum energy per unit area we are forced to introduce mass counterterms. A Riemann mass appears, which is the correction to the mass of the field generated by the nontrivial zeros of the Riemann zeta function.
Net zero building energy conservation
NASA Astrophysics Data System (ADS)
Kadam, Rohit
This research deals with energy studies performed as part of a net-zero energy study for buildings. Measured data of actual energy utilization by a building for a continuous period of 33 months was collected and studied. The peak design day on which the building consumes maximum energy was found. The averages of the energy consumption for the peak month were determined. The DOE EnergyPlus software was used to simulate the energy requirements for the building and also obtain peak energy requirements for the peak month. Alternative energy sources such as ground source heat pump, solar photovoltaic (PV) panels and day-lighting modifications were applied to redesign the energy consumption for the building towards meeting net-zero energy requirements. The present energy use by the building, DOE Energy software simulations for the building as well as the net-zero model for the building were studied. The extents of the contributions of the individual energy harvesting measures were studied. For meeting Net Zero Energy requirement, it was found that the total energy load for the building can be distributed between alternative energy methods as 5.4% to daylighting modifications, 58% to geothermal and 36.6% to solar photovoltaic panels for electricity supply and thermal energy. Thus the directions to proceed towards achieving complete net-zero energy status were identified.
Shear waves in inhomogeneous, compressible fluids in a gravity field.
Godin, Oleg A
2014-03-01
While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere. PMID:24606251
NASA Technical Reports Server (NTRS)
Gundersen, R. T.; Bond, R. L.
1976-01-01
Zero-g workstations were designed throughout manned spaceflight, based on different criteria and requirements for different programs. The history of design of these workstations is presented along with a thorough evaluation of selected Skylab workstations (the best zero-g experience available on the subject). The results were applied to on-going and future programs, with special emphasis on the correlation of neutral body posture in zero-g to workstation design. Where selected samples of shuttle orbiter workstations are shown as currently designed and compared to experience gained during prior programs in terms of man machine interface design, the evaluations were done in a generic sense to show the methods of applying evaluative techniques.
ZERI: Zero Emissions Research Initiative
NSDL National Science Digital Library
Sponsored by the Zero Emissions Research Foundation based in Geneva, Switzerland, ZERI seeks to support industry's transformation to zero emission operations. ZERI advocates either full use of inputs in an industry's own final product or conversion of the inputs for use by other industries or processes. At the site, the user can get information about the fourth Annual World ZERI Congress, read research articles and reports, or learn about ZERI's Worldwide Projects. The site also provides access to other ZERI sites in Brazil, Mexico, Namibia, Japan, and Germany.
From gravity and the organism to gravity and the cell.
Brown, A H
1991-07-01
This workshop on Gravity and the Cell was modeled on a 1968 conference on Gravity and the Organism. Each conference tried to identify the most salient scientific questions about how gravity is important to living systems. In the roughly two decades between the conferences there have been impressive advances in experimental methods, but the major scientific questions that have driven their applications to problems of gravitational biology, i.e., our broad research goals, remain much the same. In the case of plant research, improvements and extensions of biochemical techniques for investigating the ways organisms use environmental (g-force) information in salubrious ways has kept pace with progress in plant biochemistry. We now know much more about the roles of organic and inorganic substances that plants employ for information transfer and growth regulation and about the avenues and mechanisms for transport of those key substances within organisms. We have seen the acceptance of a "local control" concept that regulation of g-responses depends critically on plasmodesmata and gap junctions which allow plants and animals to throttle the transport of growth regulators across tissue boundaries often, especially in the case of plants, far removed from the morphological regions of concentration of statocytes that were once thought to be the exclusive bioaccelerometers used by plants. NASA's sponsorship of ground-based research in gravitational biology has served as important underpinning for orbital flight programs in space biology. The currently most noteworthy research area of ignorance is the mechanism by which the physical event of g-force susception becomes the biological process of g-force perception. Only rarely has it been possible to perform a definitive test of a theory of mechanism of gravity perception. Therefore, experimental research efforts in gravitational physiology still are essentially dependent on exploratory studies for which stimulus/response experiments require experimental manipulation of test subjects' g-force environment. Many research efforts have focused narrowly on contrasting the responses of test subjects to only two gravitational environments, 1 g versus real or simulated zero g. Much less effort has been devoted to studies at other g levels. For experiments in gravitational physiology three rotating machines have made, and no doubt will continue to make, important contributions: the centrifuge, the clinostat, and, most of all, the orbiting space vehicle. Some research trends, viewpoints, and shifts of emphasis are discussed. PMID:11537184
Groth, Clinton P. T.
Effects of gravity and pressure on laminar coflow methaneair diffusion flames at pressures from 1 to 60 atmospheres Marc R.J. Charest , Clinton P.T. Groth, Ömer L. Gülder University of Toronto January 2011 Available online 12 February 2011 Keywords: High pressure combustion Zero-gravity combustion
Zero Stiffness Tensegrity Structures M. Schenk a
Guest, Simon
Zero Stiffness Tensegrity Structures M. Schenk a S.D. Guest b, J.L. Herder a aMechanical, Maritime members with a zero rest length allow the construction of tensegrity struc- tures that are in equilibrium, they have zero stiffness. The zero-stiffness modes are not internal mechanisms, as they involve first
Fermion Zero Modes for Abelian BPS Monopoles
Bobby Cheng; Chris Ford
2013-02-12
Fermion zero modes for abelian BPS monopoles are considered. In the spherically symmetric case the normalisable zero modes are determined for arbitrary monopole charge N. If N>1 the zero modes are zero along $N-1$ half-lines emanating from the monopole.
Unified theory of nonlinear electrodynamics and gravity
Torres-Gomez, Alexander; Krasnov, Kirill; Scarinci, Carlos [School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)
2011-01-15
We describe a class of unified theories of electromagnetism and gravity. The Lagrangian is of the BF type, with a potential for the B field, the gauge group is U(2) (complexified). Given a choice of the potential function the theory is a deformation of (complex) general relativity and electromagnetism, and describes just two propagating polarizations of the graviton and two of the photon. When gravity is switched off the theory becomes the usual nonlinear electrodynamics with a general structure function. The Einstein-Maxwell theory can be recovered by sending some of the parameters of the defining potential to zero, but for any generic choice of the potential the theory is indistinguishable from Einstein-Maxwell at low energies. A real theory is obtained by imposing suitable reality conditions. We also study the spherically-symmetric solution and show how the usual Reissner-Nordstrom solution is recovered.
Modified gravity and large scale flows
NASA Astrophysics Data System (ADS)
Mould, Jeremy; Colless, Matthew; Erdo?du, Pirin; Jones, Heath; Lucey, John; Ma, Yin-Zhe; Magoulas, Christina; Springob, Christopher M.
2015-06-01
Reconstruction of the local velocity field from the overdensity field and a gravitational acceleration that falls off from a point mass as r -2 yields velocities in broad agreement with peculiar velocities measured with galaxy distance indicators. MONDian gravity does not. To quantify this, we introduce the velocity angular correlation function as a diagnostic of peculiar velocity field alignment and coherence as a function of scale. It is independent of the bias parameter of structure formation in the standard model of cosmology and the acceleration parameter of MOND. A modified gravity acceleration consistent with observed large scale structure would need to asymptote to zero at large distances more like r -2, than r -1.
Canonical gravity with fermions
Bojowald, Martin; Das, Rupam [Institute for Gravitation and the Cosmos, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 and Institute for Gravitation and the Cosmos, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States)
2008-09-15
Canonical gravity in real Ashtekar-Barbero variables is generalized to allow for fermionic matter. The resulting torsion changes several expressions in Holst's original vacuum analysis, which are summarized here. This in turn requires adaptations to the known loop quantization of gravity coupled to fermions, which is discussed on the basis of the classical analysis. As a result, parity invariance is not manifestly realized in loop quantum gravity.
NSDL National Science Digital Library
2012-06-26
In this activity about center of gravity (page 23 of PDF), learners investigate how the body adjusts to the force of gravity to remain balanced. In part 1, learners use different amounts of weight and meter sticks to explore balance and stability. In part 2, learners will conduct two experiments to explore their own centers of gravity. This guide includes background information, extensions, and data sheets.
NSDL National Science Digital Library
Integrated Teaching and Learning Program,
Students write a biographical sketch of an artist or athlete who lives on the edge, riding the gravity wave, to better understand how these artists and athletes work with gravity and manage risk. Note: The literacy activities for the Mechanics unit are based on physical themes that have broad application to our experience in the world concepts of rhythm, balance, spin, gravity, levity, inertia, momentum, friction, stress and tension.
Carlo Rovelli
1997-01-01
The problem of finding the quantum theory of the gravitational field, and\\u000athus understanding what is quantum spacetime, is still open. One of the most\\u000aactive of the current approaches is loop quantum gravity. Loop quantum gravity\\u000ais a mathematically well-defined, non-perturbative and background independent\\u000aquantization of general relativity, with its conventional matter couplings. The\\u000aresearch in loop quantum gravity
Gribov ambiguity in asymptotically AdS three-dimensional gravity
Anabalon, Andres [Departamento de Ciencias, Facultad de Artes Liberales, Facultad de Ingenieria y Ciencias, Universidad Adolfo Ibanez, Vina Del Mar (Chile); Canfora, Fabrizio [Centro de Estudios Cientificos (CECS), Casilla 1469, Valdivia (Chile); Giacomini, Alex; Oliva, Julio [Instituto de Fisica, Facultad de Ciencias, Universidad Austral de Chile, Valdivia (Chile)
2011-03-15
In this paper the zero modes of the de Donder gauge Faddeev-Popov operator for three-dimensional gravity with negative cosmological constant are analyzed. It is found that the AdS{sub 3} vacuum produces (infinitely many) normalizable smooth zero modes of the Faddeev-Popov operator. On the other hand, it is found that the Banados-Teitelboim-Zanelli black hole (including the zero mass black hole) does not generate zero modes. This differs from the usual Gribov problem in QCD where, close to the maximally symmetric vacuum, the Faddeev-Popov determinant is positive definite while 'far enough' from the vacuum it can vanish. This suggests that the zero mass Banados-Teitelboim-Zanelli black hole could be a suitable ground state of three-dimensional gravity with negative cosmological constant. Because of the kinematic origin of this result, it also applies for other covariant gravity theories in three dimensions with AdS{sub 3} as maximally symmetric solution, such as new massive gravity and topologically massive gravity. The relevance of these results for supersymmetry breaking is pointed out.
Extended gravity from noncommutativity
Paolo Aschieri
2012-07-20
We review the first order theory of gravity (vierbein formulation) on noncommutative spacetime studied in [1, 2]. The first order formalism allows to couple the theory to fermions. This NC action is then reinterpreted (using the Seiberg-Witten map) as a gravity theory on commutative spacetime that contains terms with higher derivatives and higher powers of the curvature and depend on the noncommutativity parameter \\theta. When the noncommutativity is switched off we recover the usual gravity action coupled to fermions. The first nontrival corrections to the usual gravity action coupled to fermions are presented in a manifest Lorentz invariant form.
ERIC Educational Resources Information Center
Axtell, M.; Stickles, J.
2010-01-01
The last ten years have seen an explosion of research in the zero-divisor graphs of commutative rings--by professional mathematicians "and" undergraduates. The objective is to find algebraic information within the geometry of these graphs. This topic is approachable by anyone with one or two semesters of abstract algebra. This article gives the
Reviewing the Zero Point Energy
Barry Setterfield
A review of recent developments in the study of the Zero Point Energy (ZPE) is made. The origin and behavior of the electromagnetic fields making up the vacuum ZPE is elucidated. From this it is deduced that the ZPE should increase with time even in a static universe such as Narliker and Arp propose. The small oscillations that a static
"Zero Tolerance" for Free Speech.
ERIC Educational Resources Information Center
Hils, Lynda
2001-01-01
Argues that school policies of "zero tolerance" of threatening speech may violate a student's First Amendment right to freedom of expression if speech is less than a "true threat." Suggests a two-step analysis to determine if student speech is a "true threat." (PKP)
ERIC Educational Resources Information Center
Geiger, Philip E.
1993-01-01
Zero-based, programmatic budgeting involves four basic steps: (1) define what needs to be done; (2) specify the resources required; (3) determine the assessment procedures and standards to use in evaluating the effectiveness of various programs; and (4) assign dollar figures to this information. (MLF)
The Zero Product Principle Error.
ERIC Educational Resources Information Center
Padula, Janice
1996-01-01
Argues that the challenge for teachers of algebra in Australia is to find ways of making the structural aspects of algebra accessible to a greater percentage of students. Uses the zero product principle to provide an example of a common student error grounded in the difficulty of understanding the structure of algebra. (DDR)
Program Planning Steps Phase Zero
Program Planning Steps Phase Zero: At the annual Council of Deans retreat, Deans and other units present two page concept papers about new academic programs which might be ready to be considered for Graduate Affairs, and the Provost discuss which of the new programs might be ready for proceeding to Phase
Stepping Back from Zero Tolerance
ERIC Educational Resources Information Center
Browne-Dianis, Judith
2011-01-01
Schools' use of zero tolerance policies has been increasing since the 1980s as part of a societal movement to crack down on drug abuse and violence among youth. But far from making schools safer, this harsh, inflexible approach to discipline has been eroding the culture of schools and creating devastating consequences for children, writes
PRETTY GOOD GRAVITY JACK MORAVA
PRETTY GOOD GRAVITY JACK MORAVA Abstract.A theory of topological gravity is a homotopy-theoretic represe* *nta- tion of the Segal. 1.Gravity categories A cobordism category has manifolds as objects, and cobordisms as morphisms
Feeling Gravity's Pull: Gravity Modeling. The Gravity Field of Mars
Frank Lemoine; David Smith; David Rowlands; Maria Zuber; G. Neumann; Douglas Chinn; D. Pavlis
2000-01-01
Most people take the constant presence of gravitys pull for granted. However, the Earth's gravitational strength actually varies from location to location. This variation occurs because mass, which influences an object's gravitational pull, is not evenly distributed within the planet. Changes in topography, such as glacial movement, an earthquake, or a rise in the ocean level, can subtly affect the
ZERO WASTE EDUCATOR -VOLUNTEER POSITION DESCRIPTION Position Title: Zero Waste Educator
Li, Ze-Nian
ZERO WASTE EDUCATOR - VOLUNTEER POSITION DESCRIPTION Position Title: Zero Waste Educator Department: SFU Sustainability Office Position Reports to (Title): Zero Waste Coordinator & Community Zero Waste Educators will assist in the launch of SFU's new Zero Waste initiative on all three SFU
NET-ZERO CARBON MANUFACTURING AT NET-ZERO COST Dustin Pohlman
Kissock, Kelly
1 NET-ZERO CARBON MANUFACTURING AT NET-ZERO COST Dustin Pohlman Industrial Assessment Center energy in manufacturing plants that results in net-zero carbon emissions at net-zero costs. The paper begins by reviewing the economics of net- zero energy buildings and discussing why a different approach
Tethered gravity laboratories study
NASA Technical Reports Server (NTRS)
Lucchetti, F.
1989-01-01
The use is studied of tether systems to improve the lowest possible steady gravity level on the Space Station. Particular emphasis is placed by the microgravity community on the achievement of high quality microgravity conditions. The tether capability is explored for active control of the center of gravity and the analysis of possible tethered configurations.
J. A. F. Gerrard; L. Strickland; A. L. Wade; H. K. Reynolds
1957-01-01
An instrument that will simulate the anomalous gravity effects of a subsurface body, having a density differing from that of its surroundings, is described. The device makes use of the similarity between the gravity equation and Lambert's cosine ? law, and enables the geophysicist to synthesize the anomaly producing body in a time much shorter than that required for conventional
Sigmund Hammer
1982-01-01
After 20 years of development efforts, the airborne gravity survey has finally become a practical exploration method. Besides gravity data, the airborne survey can also collect simultaneous, continuous records of high-precision magneticfield data as well as terrain clearance; these provide a topographic contour map useful in calculating terrain conditions and in subsequent planning and engineering. Compared with a seismic survey,
NSDL National Science Digital Library
2014-09-18
Students use water balloons and a length of string to understand how the force of gravity between two objects and the velocity of a spacecraft can balance to form an orbit. They see that when the velocity becomes too great for gravity to hold the spacecraft in orbit, the object escapes the orbit and travels further away from the planet.
Tethered gravity laboratories study
NASA Technical Reports Server (NTRS)
Lucchetti, F.
1989-01-01
Information on the Tethered Gravity Laboratory on the International Space Station is given in viewgraph form. Topics covered include active control, low gravity processes identification, systems analysis, tether interfaces with the Laboratory, elevator and payload configurations, elevator subsystems, and accelerometer technology requirements.
Antoniadis, Ignatios
2003-01-01
We discuss a string-theory-derived mechanism for localized gravity, which produces a deviation from Newton's law of gravitation at cosmological distances. This communication is based on the paper [1] (Non-compact Calabi-Yau manifolds and localized gravity) by Ruben Minasian and the present authors.
Ultraviolet Complete Quantum Gravity
J. W. Moffat
2011-04-18
An ultraviolet complete quantum gravity theory is formulated in which vertex functions in Feynman graphs are entire functions and the propagating graviton is described by a local, causal propagator. The cosmological constant problem is investigated in the context of the ultraviolet complete quantum gravity.
Torsion of Space-time in f(R) gravity
Majid Mohsenzadeh; Ebrahim Yusofi
2012-07-07
In this paper, we first review some aspects of the f(R) gravity and then the concept of torsion of space-time due to metric-affine formalism in f(R) gravity is studied. Within this formalism in which the matter action is supposed to dependent on the connection, we achieve to interesting cases including non-zero torsion tensor. Then with the physical interpretation of torsion of space-time in high energy limit, the modified expression of Mach's principle in a very strong gravitational region is obtained.
Containment of a silicone fluid free surface in reduced gravity
NASA Technical Reports Server (NTRS)
Pline, A.; Jacobson, T.
1988-01-01
In support of the surface tension driven convection experiment planned for flight aboard the Space Shuttle, tests were conducted under reduced gravity in the 2.2-sec drop tower and the 5.0-sec Zero-G facility at the Lewis Research Center. The dynamics of controlling the test fluid, a 10-centistoke viscosity silicone fluid, in a low-gravity environment were investigated using different container designs and barrier coatings. Three container edge designs were tested without a barrier coating: a square edge, a sharp edge with a 45-deg slope, and a saw-tooth edge. All three edge designs were successful in containing the fluid below the edge.
NASA Astrophysics Data System (ADS)
Linder, E. V.
2014-03-01
Gravity directs the paths of light rays and the growth of structure. Moreover, gravity on cosmological scales does not simply point down: It accelerates the universal expansion by pulling outward, either due to a highly negative pressure dark energy or an extension of general relativity. We have examined methods to test the properties of gravity through cosmological measurements. We have then considered specific possibilities for a sound gravitational theory based on the Galilean shift symmetry. The evolution of the laws of gravity from the early universe to the present acceleration to the future fate - the paths of gravity - carries rich information on this fundamental force of physics, and on the mystery of dark energy.
Gravitomagnetism in Massive Gravity
Tasseten, Kezban
2015-01-01
Massive gravity in the weak field limit is described by the Fierz-Pauli theory with 5 degrees of freedom in four dimensions. In this theory, we calculate the gravitomagnetic effects (potential energy) between two point-like, spinning sources that also orbit around each other in the limit where the spins and the velocities are small. Spin-spin, spin-orbit and orbit-orbit interactions in massive gravity theory have rather remarkable, discrete differences from their counterparts in General Relativity. Our computation is applicable for large distances, for example, for interaction between galaxies or galaxy clusters where massive gravity is expected to play a role. We also extend the computations to quadratic gravity theories in four dimensions and find the lowest order gravitomagnetic effects and show that at small separations quadratic gravity behaves differently than General Relativity.
NSDL National Science Digital Library
This broadcast reports on Gravity Probe B, a satellite designed to test the frame dragging prediction of Einstein's theory of general relativity, where a spinning object such as the Earth will push spacetime in front of it. Gravity Probe B uses gyroscopes which will shift direction while orbiting the Earth (if general relativity is correct). The broadcast contains comments from a scientist who has worked on the Gravity Probe B mission for over 44 years. There is a brief explanation of the difference between the behavior of gravity in Newtonian physics and general relativity. The broadcast also discusses why it took so long to build the satellite (a dozen technologies had to be invented first), the cost involved, and whether the plug would be pulled on the mission; however, Gravity Probe B was finally launched on April 20, 2004. The broadcast is 30 minutes in length.
Moving Toward Zero Energy Buildings
Ginsberg, M.
2008-01-01
, labeling programs, lighting research, solar and geothermal heat pumps are all part of a bigger goal: zero energy buildings. To achieve them, we need the world?s best energy efficiency components (lighting, insulation, windows, heating, cooling..., appliances, etc) and systems integration to optimize the performance of the building. Then we need the best renewable energy technologies that can be incorporated into buildings: solar, small wind, and geothermal heat pumps (some day hydrogen storage...
Disposable remote zero headspace extractor
Hand, Julie J. (Idaho Falls, ID); Roberts, Mark P. (Arco, ID)
2006-03-21
The remote zero headspace extractor uses a sampling container inside a stainless steel vessel to perform toxicity characteristics leaching procedure to analyze volatile organic compounds. The system uses an in line filter for ease of replacement. This eliminates cleaning and disassembly of the extractor. All connections are made with quick connect fittings which can be easily replaced. After use, the bag can be removed and disposed of, and a new sampling container is inserted for the next extraction.
Solving discrete zero point problems
Gerard Van Der Laan; D. A. J. J. Talman; Zaifu Yang
2006-01-01
In this paper we present two theorems on the existence of a discrete zero point of a function from the n-dimensional integer lattice ?n to the n-dimensional Euclidean space ?n. The theorems differ in their boundary conditions. For both theorems we give a proof using a combinatorial lemma and present\\u000a a constructive proof based on a simplicial algorithm that finds
Location of zeros of polynomials
Chadia Affane-Aji; Neha Agarwal; N. K. Govil
2009-01-01
In this paper, we obtain a result concerning the location of zeros of a polynomial p(z)=a0+a1z+a2z2+?+anzn, where ais are complex coefficients and z is a complex variable. This result sharpens Cauchys result, along with some of the other known results which were based on the classical Cauchys work. Moreover, a MATLAB code is developed to construct polynomials, and compare the
Zax, D.B.; Bielecki, A.; Zilm, K.W.; Pines, A.; Weitekamp, D.P.
1985-11-15
Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for /sup 1/H, /sup 2/D, /sup 7/Li, /sup 13/C, and /sup 27/Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra.
NASA Technical Reports Server (NTRS)
Burleigh, Scott C.
2011-01-01
Zero-Copy Objects System software enables application data to be encapsulated in layers of communication protocol without being copied. Indirect referencing enables application source data, either in memory or in a file, to be encapsulated in place within an unlimited number of protocol headers and/or trailers. Zero-copy objects (ZCOs) are abstract data access representations designed to minimize I/O (input/output) in the encapsulation of application source data within one or more layers of communication protocol structure. They are constructed within the heap space of a Simple Data Recorder (SDR) data store to which all participating layers of the stack must have access. Each ZCO contains general information enabling access to the core source data object (an item of application data), together with (a) a linked list of zero or more specific extents that reference portions of this source data object, and (b) linked lists of protocol header and trailer capsules. The concatenation of the headers (in ascending stack sequence), the source data object extents, and the trailers (in descending stack sequence) constitute the transmitted data object constructed from the ZCO. This scheme enables a source data object to be encapsulated in a succession of protocol layers without ever having to be copied from a buffer at one layer of the protocol stack to an encapsulating buffer at a lower layer of the stack. For large source data objects, the savings in copy time and reduction in memory consumption may be considerable.
Relativistic Dipole Matrix Element Zeros
NASA Astrophysics Data System (ADS)
Lajohn, L. A.; Pratt, R. H.
2002-05-01
There is a special class of relativistic high energy dipole matrix element zeros (RZ), whose positions with respect to photon energy ? , only depend on the bound state l quantum number according to ?^0=mc^2/(l_b+1) (independent of primary quantum number n, nuclear charge Z, central potential V and dipole retardation). These RZ only occur in (n,l_b,j_b)arrow (? , l_b+1,j_b) transitions such as ns_1/2arrow ? p_1/2; np_3/2arrow ? d_3/2: nd_5/2arrow ? f_5/2 etc. The nonrelativistic limit of these matrix elements can be established explicitly in the Coulomb case. Within the general matrix element formalism (such as that in [1]); when |? | is substituted for ? in analytic expressions for matrix elements, the zeros remain, but ?^0 now becomes dependent on n and Z. When the reduction to nonrelativistic form is completed by application of the low energy approximation ? mc^2 mc^2, the zeros disappear. This nonzero behavior was noted in nonrelativistic dipole Coulomb matrix elements by Fano and Cooper [2] and later proven by Oh and Pratt[3]. (J. H. Scofield, Phys. Rev. A 40), 3054 (1989 (U. Fano and J. W. Cooper, Rev. Mod. Phys. 40), 441 (1968). (D. Oh and R. H. Pratt, Phys. Rev. A 34), 2486 (1986); 37, 1524 (1988); 45, 1583 (1992).
Probability around the Quantum Gravity. Part 1: Planar Pure Gravity
Probability around the Quantum Gravity. Part 1: Planar Pure Gravity V.A.Malyshev \\Lambda September 17, 1998 Abstract In this paper we study stochastic dynamics which leaves quantum gravity equilibrium science and biology. At the same time the paper can serve an intro duction to quantum gravity
Chern Simons formulation of three-dimensional gravity with torsion and nonmetricity
NASA Astrophysics Data System (ADS)
Cacciatori, Sergio L.; Caldarelli, Marco M.; Giacomini, Alex; Klemm, Dietmar; Mansi, Diego S.
2006-12-01
We consider various models of three-dimensional gravity with torsion or nonmetricity (metric affine gravity), and show that they can be written as Chern-Simons theories with suitable gauge groups. Using the groups ISO(2,1), SL(2,C) and SL(2,R)×SL(2,R), and the fact that they admit two independent coupling constants, we obtain the Mielke-Baekler model for zero, positive and negative effective cosmological constant respectively. Choosing SO(3,2) as the gauge group, one gets a generalization of conformal gravity that has zero torsion and only the trace part of the nonmetricity. This characterizes a Weyl structure. Finally, we present a new topological model of metric affine gravity in three dimensions arising from an SL(4,R) Chern-Simons theory.
Effects of background gravity stimuli on gravity-controlled behavior
NASA Technical Reports Server (NTRS)
Mccoy, D. F.
1976-01-01
Physiological and developmental effects of altered gravity were researched. The stimulus properties of gravity have been found to possess reinforcing and aversive properties. Experimental approaches taken, used animals placed into fields of artificial gravity, in the form of parabolic or spiral centrifuges. Gravity preferences were noted and it was concluded that the psychophysics of gravity and background factors which support these behaviors should be further explored.
MANEUVER REGULATION, TRANSVERSE FEEDBACK LINEARIZATION, AND ZERO
Maggiore, Manfredi
MANEUVER REGULATION, TRANSVERSE FEEDBACK LINEARIZATION, AND ZERO DYNAMICS Chris Nielsen,1 Manfredi focus is on output maneuver regulation where stabilizing transverse dynamics is a key requirement. Keywords: Maneuver regulation, path following, feedback linearization, zero dynamics, non-square systems
PRETTY GOOD GRAVITY JACK MORAVA
PRETTY GOOD GRAVITY JACK MORAVA Abstract. A theory of topological gravity is a homotopy of Donaldson theory. 1. Gravity categories A cobordism category has manifolds as objects, and cobordisms of certain closely related twocategories; the definition below is based on her ideas. Definition A gravity
PRETTY GOOD GRAVITY JACK MORAVA
PRETTY GOOD GRAVITY JACK MORAVA Abstract. A theory of topological gravity is a homotopy of Donaldson theory. 1. Gravity categories A cobordism category has manifolds as objects, and cobordisms of certain closely related two-categories; the definition below is based on her ideas. Definition A gravity
Toroidal solutions in Horava Gravity
Ahmad Ghodsi
2011-02-24
Recently a new four-dimensional non relativistic renormalizable theory of gravity was proposed by Horava. This gravity reduces to Einstein gravity at large distances. In this paper by using the new action for gravity we present different toroidal solutions to the equations of motion. Our solutions describe the near horizon geometry with slow rotating parameter.
NSDL National Science Digital Library
George Nelson
2004-09-01
We all know lots of sayings about gravity. "What goes up must come down." "You fail to understand the gravity of the situation." Gravity is the name we give to the phenomenon that any two masses, like you and the earth, that attract each other. This brief introduction to gravity will help elementary educators teach the concept with confidence.
Finite Zero Point Gravitational Energy in the context of Modified Dispersion Relations
Remo Garattini; Gianluca Mandanici
2013-01-02
We compute the Zero Point Energy in a spherically symmetric background distorted at high energy as predicted by Gravity's Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. We find that the ordinary divergences can here be handled by an appropriate choice of the rainbow's functions, in contrast to what happens in other conventional approaches.
Finite Zero Point Gravitational Energy in the Context of Modified Dispersion Relations
NASA Astrophysics Data System (ADS)
Garattini, Remo; Mandanici, Gianluca
2015-01-01
We compute the Zero Point Energy in a spherically symmetric background distorted at high energy as predicted by Gravity's Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. We find that the ordinary divergences can here be handled by an appropriate choice of the rainbow's functions, in contrast to what happens in other conventional approaches.
A Lifshitz Black Hole in Four Dimensional R^2 Gravity
Cai, Rong-Gen; Sun, Ya-Wen
2009-01-01
We consider a higher derivative gravity theory in four dimensions with a negative cosmological constant and show that vacuum solutions of both Lifshitz type and Schr\\"{o}dinger type with arbitrary dynamical exponent z exist in this system. Then we find an analytic black hole solution which asymptotes to the vacuum Lifshitz solution with z=3/2 at a specific value of the coupling constant. We analyze the thermodynamic behavior of this black hole and find that the black hole has zero entropy while non-zero temperature, which is very similar to the case of BTZ black holes in new massive gravity at a specific coupling. In addition, we find that the three dimensional Lifshitz black hole recently found by E. Ayon-Beato et al. has a negative entropy and mass when the Newton constant is taken to be positive.
Hammer, S.
1982-01-11
After 20 years of development efforts, the airborne gravity survey has finally become a practical exploration method. Besides gravity data, the airborne survey can also collect simultaneous, continuous records of high-precision magneticfield data as well as terrain clearance; these provide a topographic contour map useful in calculating terrain conditions and in subsequent planning and engineering. Compared with a seismic survey, the airborne gravity method can cover the same area much more quickly and cheaply; a seismograph could then detail the interesting spots.
Zygmunt Lalak; Stefan Pokorski; Krzysztof Turzynski
2008-08-18
We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for mu and Bmu generation. Gravity sector can include stabilized moduli.
Ning Wu
2001-10-30
The quantum gravity is formulated based on principle of local gauge invariance. The model discussed in this paper has local gravitational gauge symmetry and gravitational field appears as gauge field. The problems on quantization and renormalization of the theory are also discussed in this paper. In leading order approximation, the gravitational gauge field theory gives out classical Newton's theory of gravity. In first order approximation and for vacuum, the gravitational gauge field theory gives out Einstein's general theory of relativity. This quantum gauge theory of gravity is a renormalizable quantum theory.
Modeling Candle Flame Behavior In Variable Gravity
NASA Technical Reports Server (NTRS)
Alsairafi, A.; Tien, J. S.; Lee, S. T.; Dietrich, D. L.; Ross, H. D.
2003-01-01
The burning of a candle, as typical non-propagating diffusion flame, has been used by a number of researchers to study the effects of electric fields on flame, spontaneous flame oscillation and flickering phenomena, and flame extinction. In normal gravity, the heat released from combustion creates buoyant convection that draws oxygen into the flame. The strength of the buoyant flow depends on the gravitational level and it is expected that the flame shape, size and candle burning rate will vary with gravity. Experimentally, there exist studies of candle burning in enhanced gravity (i.e. higher than normal earth gravity, g(sub e)), and in microgravity in drop towers and space-based facilities. There are, however, no reported experimental data on candle burning in partial gravity (g < g(sub e)). In a previous numerical model of the candle flame, buoyant forces were neglected. The treatment of momentum equation was simplified using a potential flow approximation. Although the predicted flame characteristics agreed well with the experimental results, the model cannot be extended to cases with buoyant flows. In addition, because of the use of potential flow, no-slip boundary condition is not satisfied on the wick surface. So there is some uncertainty on the accuracy of the predicted flow field. In the present modeling effort, the full Navier-Stokes momentum equations with body force term is included. This enables us to study the effect of gravity on candle flames (with zero gravity as the limiting case). In addition, we consider radiation effects in more detail by solving the radiation transfer equation. In the previous study, flame radiation is treated as a simple loss term in the energy equation. Emphasis of the present model is on the gas-phase processes. Therefore, the detailed heat and mass transfer phenomena inside the porous wick are not treated. Instead, it is assumed that a thin layer of liquid fuel coated the entire wick surface during the burning process. This is the limiting case that the mass transfer process in the wick is much faster than the evaporation process at the wick surface.
Propulsion Investigation for Zero and Near-Zero Emissions Aircraft
NASA Technical Reports Server (NTRS)
Snyder, Christopher A.; Berton, Jeffrey J.; Brown, Gerald v.; Dolce, James L.; Dravid, Marayan V.; Eichenberg, Dennis J.; Freeh, Joshua E.; Gallo, Christopher A.; Jones, Scott M.; Kundu, Krishna P.; Marek, Cecil J.; Millis, Marc G.; Murthy, Pappu L.; Roach, Timothy M.; Smith, Timothy D.; Stefko, George L.; Sullivan, Roy M.; Tornabene, Robert T.; Geiselhat, Karl A.; Kascak, Albert F.
2009-01-01
As world emissions are further scrutinized to identify areas for improvement, aviation s contribution to the problem can no longer be ignored. Previous studies for zero or near-zero emissions aircraft suggest aircraft and propulsion system sizes that would perform propulsion system and subsystems layout and propellant tankage analyses to verify the weight-scaling relationships. These efforts could be used to identify and guide subsequent work on systems and subsystems to achieve viable aircraft system emissions goals. Previous work quickly focused these efforts on propulsion systems for 70- and 100-passenger aircraft. Propulsion systems modeled included hydrogen-fueled gas turbines and fuel cells; some preliminary estimates combined these two systems. Hydrogen gas-turbine engines, with advanced combustor technology, could realize significant reductions in nitrogen emissions. Hydrogen fuel cell propulsion systems were further laid out, and more detailed analysis identified systems needed and weight goals for a viable overall system weight. Results show significant, necessary reductions in overall weight, predominantly on the fuel cell stack, and power management and distribution subsystems to achieve reasonable overall aircraft sizes and weights. Preliminary conceptual analyses for a combination of gas-turbine and fuel cell systems were also performed, and further studies were recommended. Using gas-turbine engines combined with fuel cell systems can reduce the fuel cell propulsion system weight, but at higher fuel usage than using the fuel cell only.
Zero point energy of renormalized Wilson loops
Yoshimasa Hidaka; Robert D. Pisarski
2009-01-01
The quark-antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to
Zero Tolerance in Tennessee Schools: An Update.
ERIC Educational Resources Information Center
Potts, Kim; Njie, Bintou; Detch, Ethel R.; Walton, Jason
As required by Tennessee law, this report examines the state's zero-tolerance disciplinary data collected by the Tennessee Department of Education for school years 1999-00, 2000-01, and 2001-02. The first section displays statewide zero-tolerance statistics. The second section focuses on the zero-tolerance statistics of Tennessee's five major
Recognising zero among implicitly defined elementary numbers
Richardson, Daniel
Recognising zero among implicitly defined elementary numbers Daniel Richardson Department which have been given previously to solve related problems, depending essentially on the zero problem for implicitly defined algebraic numbers. Key words: Exp-Log constants, zero test, Schanuel conjecture, interval
Zero Tolerance: Advantages and Disadvantages. Research Brief
ERIC Educational Resources Information Center
Walker, Karen
2009-01-01
What are the positives and negatives of zero tolerance? What should be considered when examining a school's program? Although there are no definitive definitions of zero tolerance, two commonly used ones are as follows: "Zero tolerance means that a school will automatically and severely punish a student for a variety of infractions" (American Bar
Romanian Zero Pronoun Distribution: A Comparative Study
Inkpen, Diana
Romanian Zero Pronoun Distribution: A Comparative Study Claudiu Mihaila1 , Iustina Ilisei2 , Diana pronouns. Anaphoric zero pronouns pose an even greater challenge, since this category is not lexically on the distribution of zero pronouns in Romanian in various genres: encyclopaedic, legal, literary, and news
ZERO DYNAMICS OF UNDERACTUATED PLANAR BIPED WALKERS
Grizzle, Jessy W.
ZERO DYNAMICS OF UNDERACTUATED PLANAR BIPED WALKERS E.R. Westervelt 1 J.W. Grizzle 1 D.E. Koditschek 2 University of Michigan, Ann Arbor, MI, USA Abstract: The zero dynamics of a hybrid model of the zero dynamics correspond to asymptotically stabilizable orbits of the full hybrid model of the walker
Zero-Content Augmented Caches Julien Dusser
Paris-Sud XI, Université de
Zero-Content Augmented Caches Julien Dusser julien.dusser@inria.fr Thomas Piquet thomas amounts of null data. Moreover these zero data often exhibit high spatial locality. On some applications on a standard cache line appears as a waste of resources. In this paper, we propose the Zero-Content Augmented
Minimal zero-dimensional extensions Fred Richman
Richman, Fred
Minimal zero-dimensional extensions Fred Richman Florida Atlantic University 16 October 2011 BesanĂ§on Richman (FAU) Minimal zero-dimensional extensions 10/16 1 / 12 #12;Chiorescu's theorem Marcela Chiorescu's theorem Richman (FAU) Minimal zero-dimensional extensions 10/16 2 / 12 #12;Chiorescu's theorem
A zero switching loss matrix converter
Ching-Tsai Pan; Tsung-Cheng Chen; Jenn-Jong Shieh
1993-01-01
A low loss bidirectional switch set is proposed for a matrix power converter. The proposed switch is able to turn on at zero current and turn off at zero voltage to achieve almost zero loss and soft switching. Hence, a simple hysteretic current control can now be applied directly to a matrix power converter without adding any additional snubber circuit
Canadian low-gravity research using parabolic aircraft
NASA Astrophysics Data System (ADS)
Campbell, Glen S.; Vezina, L.; Aitken, J. F.
1992-12-01
An active experimental program being implemented by Canada in microgravity, which relies heavily on the use of parabolic aircraft, is discussed. The advantages of zero-gravity aircraft include low cost and quick turnaround. These aircraft have demonstrated their value for prototyping experimental hardware developments planned for flight at other facilities, such as sounding rockets and Shuttle-based carriers which are supported by the Canadian Space Agency.
New energy definition for higher-curvature gravities
S. Deser; Bayram Tekin
2007-01-01
We propose a novel but natural definition of conserved quantities for gravity models of quadratic and higher order in curvature. Based on the spatial asymptotics of curvature rather than of metric, it avoids the more egregious problems---such as zero-energy ``theorems'' and failure in flat backgrounds---in this fourth-derivative realm. In D>4, the present expression indeed correctly discriminates between second-derivative Gauss-Bonnet and
New energy definition for higher-curvature gravities
Bayram Tekin; S. Deser
2007-01-01
We propose a novel but natural definition of conserved quantities for gravity models of quadratic and higher order in curvature. Based on the spatial asymptotics of curvature rather than of metric, it avoids the more egregious problems - such as zero-energy 'theorems' and failure in flat backgrounds--in this fourth-derivative realm. In D>4, the present expression indeed correctly discriminates between second-derivative
Zero-G experiments in two-phase fluids flow regimes
NASA Technical Reports Server (NTRS)
Heppner, D. B.; King, C. D.; Littles, J. W.
1975-01-01
The two-phase flows studied were liquid and gas mixtures in a straight flow channel of circular cross-section. Boundaries between flow regimes have been defined for normogravity on coordinates of gas quality and total mass velocity; and, when combined with boundary expressions having a Froude number term, an analytical model was derived predicting boundary shifts with changes in gravity level. Experiments with air and water were performed, first in the normogravity environment of a ground laboratory and then in 'zero gravity' aboard a KC-135 aircraft flying parabolic trajectories. Data reduction confirmed regime boundary shifts in the direction predicted, although the magnitude was a little less than predicted. Pressure drop measurements showed significant increases for the low gravity condition.
Zero energy modes in heterostructures
NASA Astrophysics Data System (ADS)
Petrescu, Tudor; Rachel, Stephan; Le Hur, Karyn
2011-03-01
Zero energy gapless modes have been realized in 1-dimensional domain walls of 2-dimensional systems. In the case of single- or bi-layer graphene, such a quantum wire can be realized by inverting the sign of the gap across a one dimensional interface, without time-reversal symmetry breaking. With the experimental realization of artificial graphene, previously unrealistic additional terms in the Hamiltonian such as staggered potential or artificial gauge fields can be exploited towards the same goal. We classify these terms and study the interplay of disorder effects and boundary conditions.
Ronquillo, M.
2014-01-01
Conference, Dallas, Texas Nov. 18-20 ? Original 5-MGD Facility Built in 1958 ? Currently Serves 23-Communities (~1M-PPL) ? Qdesign=166-MGD; Qaverage=105-MGD ? Single-Stage, Activated Sludge w/Nitrification ? Anaerobic Digestion of Wastewater Solids 2 Fort... Conference, Dallas, Texas Nov. 18-20 10 Journey to Net Zero began in the 1960s Digester Gas fueled Engine Blowers & Generators Some heat recovery for anaerobic digesters ESL-KT-14-11-47 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas...
Gary T. Horowitz; Joseph Polchinski
2006-01-01
We review the emergence of gravity from gauge theory in the context of AdS\\/CFT duality. We discuss the evidence for the duality, its lessons for gravitational physics, generalizations, and open questions.
Bhattacharya, Swastik
2015-01-01
General theory of relativity (or Lovelock extensions) is a dynamical theory; given an initial configuration on a space-like hypersurface, it makes a definite prediction of the final configuration. Recent developments suggest that gravity may be described in terms of macroscopic parameters. It finds a concrete manifestation in the fluid-gravity correspondence. Most of the efforts till date has been to relate equilibrium configurations in gravity with fluid variables. In order for the emergent paradigm to be truly successful, it has to provide a statistical mechanical derivation of how a given initial static configuration evolves into another. In this essay, we show that the energy transport equation governed by the fluctuations of the horizon-fluid is similar to Raychaudhuri equation and, hence gravity is truly emergent.
ERIC Educational Resources Information Center
Nelson, George
2004-01-01
Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of
Gianluca Calcagni
2011-02-09
Despite their diversity, many of the most prominent candidate theories of quantum gravity share the property to be effectively lower-dimensional at small scales. In particular, dimension two plays a fundamental role in the finiteness of these models of Nature. Thus motivated, we entertain the idea that spacetime is a multifractal with integer dimension 4 at large scales, while it is two-dimensional in the ultraviolet. Consequences for particle physics, gravity and cosmology are discussed.
Zero point energy of renormalized Wilson loops
Hidaka, Yoshimasa [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Pisarski, Robert D. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)
2009-10-01
The quark-antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to the zero point energy vanishes in the Nambu model, but is nonzero when terms for extrinsic curvature are included. At one loop order, the nonperturbative contribution to the zero point energy is negative, regardless of the sign of the extrinsic curvature term.
Dirac cone and double zero materials
Chan, C. T.; Huang Xueqin; Hang Zhihong; Zheng Huihuo [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Lai Yun [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Department of Physics, Soochow University, 1 Shizi Street, Suzhou 215006 (China)
2011-10-03
Materials with zero permittivity and zero permeability (double zero) possess very interesting wave manipulation characteristics. Systems with Dirac cones in the band structure also possess amazing wave transport properties. These two classes of material are actually related to each other. We show that dielectric photonic crystals can be designed and fabricated which exhibit Dirac cones at k = 0 at a finite frequency. A subset of such materials behave as if they have zero permittivity and zero permeability at the Dirac point, as well as exhibiting properties intrinsic to a Dirac cone.
New Massive Gravity and AdS{sub 4} Counterterms
Jatkar, Dileep P. [Harish-Chandra Research Institute, Chhatnag Road, Jhusi, Allahabad, 211019 (India); Sinha, Aninda [Centre for High Energy Physics, Indian Institute of Science, C. V. Raman Avenue, Bangalore 560012 (India)
2011-04-29
We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS{sub 4}). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS{sub 4} Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS{sub 3} gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory.
Asymptotic safety of gravity and the Higgs boson mass
Mikhail Shaposhnikov; Christof Wetterich
2010-01-12
There are indications that gravity is asymptotically safe. The Standard Model (SM) plus gravity could be valid up to arbitrarily high energies. Supposing that this is indeed the case and assuming that there are no intermediate energy scales between the Fermi and Planck scales we address the question of whether the mass of the Higgs boson $m_H$ can be predicted. For a positive gravity induced anomalous dimension $A_\\lambda>0$ the running of the quartic scalar self interaction $\\lambda$ at scales beyond the Planck mass is determined by a fixed point at zero. This results in $m_H=m_{\\rm min}=126$ GeV, with only a few GeV uncertainty. This prediction is independent of the details of the short distance running and holds for a wide class of extensions of the SM as well. For $A_\\lambda 0$ is favored by explicit computations existing in the literature.
NASA Technical Reports Server (NTRS)
Capps, Stephen; Lorandos, Jason; Akhidime, Eval; Bunch, Michael; Lund, Denise; Moore, Nathan; Murakawa, Kiosuke
1989-01-01
The purpose of this study is to investigate comprehensive design requirements associated with designing habitats for humans in a partial gravity environment, then to apply them to a lunar base design. Other potential sites for application include planetary surfaces such as Mars, variable-gravity research facilities, and a rotating spacecraft. Design requirements for partial gravity environments include locomotion changes in less than normal earth gravity; facility design issues, such as interior configuration, module diameter, and geometry; and volumetric requirements based on the previous as well as psychological issues involved in prolonged isolation. For application to a lunar base, it is necessary to study the exterior architecture and configuration to insure optimum circulation patterns while providing dual egress; radiation protection issues are addressed to provide a safe and healthy environment for the crew; and finally, the overall site is studied to locate all associated facilities in context with the habitat. Mission planning is not the purpose of this study; therefore, a Lockheed scenario is used as an outline for the lunar base application, which is then modified to meet the project needs. The goal of this report is to formulate facts on human reactions to partial gravity environments, derive design requirements based on these facts, and apply the requirements to a partial gravity situation which, for this study, was a lunar base.
Cage on zero Curiously enough, the twelve-tone system has no zero in it. Given
Cameron, Peter
Cage on zero Curiously enough, the twelve-tone system has no zero in it. Given a series: 3, 5, 2, 7. For in this system 12 plus 12 equals 12. There is not enough of zero in it. John Cage, "Eric Satie", Silence: Lectures and Writings, Calder and Boyars, 1968. I contend that Cage is confusing two different zeros
Feasibility of Achieving Net-Zero-Energy Net-Zero-Cost
1 Feasibility of Achieving Net- Zero-Energy Net-Zero-Cost Homes I.S. Walker, Al-Beaini, SSimjanovic,JohnStanley,BretStrogen,IainWalker FeasibilityofAchieving ZeroNetEnergy,Zero NetCostHomes #12;4 ACKNOWLEDGEMENTS
NASA Astrophysics Data System (ADS)
Gammaitoni, Luca; Chiuchiú, D.; Madami, M.; Carlotti, G.
2015-06-01
Is it possible to operate a computing device with zero energy expenditure? This question, once considered just an academic dilemma, has recently become strategic for the future of information and communication technology. In fact, in the last forty years the semiconductor industry has been driven by its ability to scale down the size of the complementary metal-oxide semiconductor-field-effect transistor, the building block of present computing devices, and to increase computing capability density up to a point where the power dissipated in heat during computation has become a serious limitation. To overcome such a limitation, since 2004 the Nanoelectronics Research Initiative has launched a grand challenge to address the fundamental limits of the physics of switches. In Europe, the European Commission has recently funded a set of projects with the aim of minimizing the energy consumption of computing. In this article we briefly review state-of-the-art zero-power computing, with special attention paid to the aspects of energy dissipation at the micro- and nanoscales.
Gammaitoni, Luca; Chiuchiú, D; Madami, M; Carlotti, G
2015-06-01
Is it possible to operate a computing device with zero energy expenditure? This question, once considered just an academic dilemma, has recently become strategic for the future of information and communication technology. In fact, in the last forty years the semiconductor industry has been driven by its ability to scale down the size of the complementary metal-oxide semiconductor-field-effect transistor, the building block of present computing devices, and to increase computing capability density up to a point where the power dissipated in heat during computation has become a serious limitation. To overcome such a limitation, since 2004 the Nanoelectronics Research Initiative has launched a grand challenge to address the fundamental limits of the physics of switches. In Europe, the European Commission has recently funded a set of projects with the aim of minimizing the energy consumption of computing. In this article we briefly review state-of-the-art zero-power computing, with special attention paid to the aspects of energy dissipation at the micro- and nanoscales. PMID:25961656
Michele Del Zotto; Jonathan J. Heckman; David R. Morrison; Daniel S. Park
2014-12-19
We study how to couple a 6D superconformal field theory (SCFT) to gravity. In F-theory, the models in question are obtained working on the supersymmetric background R^{5,1} x B where B is the base of a compact elliptically fibered Calabi-Yau threefold in which two-cycles have contracted to zero size. When the base has orbifold singularities, we find that the anomaly polynomial of the 6D SCFTs can be understood purely in terms of the intersection theory of fractional divisors: the anomaly coefficient vectors are identified with elements of the orbifold homology. This also explains why in certain cases, the SCFT can appear to contribute a "fraction of a hypermultiplet" to the anomaly polynomial. Quantization of the lattice of string charges also predicts the existence of additional light states beyond those captured by such fractional divisors. This amounts to a refinement to the lattice of divisors in the resolved geometry. We illustrate these general considerations with explicit examples, focusing on the case of F-theory on an elliptic Calabi-Yau threefold with base P^2 / Z_3.
Quantum-Gravity Fluctuations and the Black-Hole Temperature
Shahar Hod
2015-05-18
Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the {\\it discrete} quantum spectrum suggested by Bekenstein with the {\\it continuous} semi-classical spectrum suggested by Hawking ? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the {\\it discrete} (quantized) black-hole radiation agrees with the well-known Hawking temperature of the {\\it continuous} (semi-classical) black-hole spectrum.
Quantum-Gravity Fluctuations and the Black-Hole Temperature
Hod, Shahar
2015-01-01
Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the {\\it discrete} quantum spectrum suggested by Bekenstein with the {\\it continuous} semi-classical spectrum suggested by Hawking ? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quanti...
Quantum-gravity fluctuations and the black-hole temperature
NASA Astrophysics Data System (ADS)
Hod, Shahar
2015-05-01
Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum.
Constraints on texture zero and cofactor zero models for neutrino mass
Whisnant, K.; Liao, Jiajun [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Marfatia, D. [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA and Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)
2014-06-24
Imposing a texture or cofactor zero on the neutrino mass matrix reduces the number of independent parameters from nine to seven. Since five parameters have been measured, only two independent parameters would remain in such models. We find the allowed regions for single texture zero and single cofactor zero models. We also find strong similarities between single texture zero models with one mass hierarchy and single cofactor zero models with the opposite mass hierarchy. We show that this correspondence can be generalized to texture-zero and cofactor-zero models with the same homogeneous costraints on the elements and cofactors.
QCD thermodynamics at zero and non-zero density
Schmidt, Christian
2015-01-01
We present results on the QCD equation of state, obtained with two different improved dynamical staggered fermion actions and almost physical quark masses. Lattice cut-off effects are discussed in detail as results for three different lattice spacings are available now, i.e. results have been obtained on lattices with temporal extent of $N_\\tau=4,6$ and 8. Furthermore we discuss the Taylor expansion approach to non-zero baryon chemical potential by means of an expansion of the pressure. We use the expansion coefficients to calculate various fluctuations and correlations among hadronic charges. We find that the correlations reproduce the qualitative behavior of the resonance gas model below $T_c$ and start to agree with the free gas predictions for $T\\gsim 1.5T_c$.
NASA Technical Reports Server (NTRS)
Argentiero, P.; Lowrey, B.
1976-01-01
The least squares collocation algorithm for estimating gravity anomalies from geodetic data is shown to be an application of the well known regression equations which provide the mean and covariance of a random vector (gravity anomalies) given a realization of a correlated random vector (geodetic data). It is also shown that the collocation solution for gravity anomalies is equivalent to the conventional least-squares-Stokes' function solution when the conventional solution utilizes properly weighted zero a priori estimates. The mathematical and physical assumptions underlying the least squares collocation estimator are described, and its numerical properties are compared with the numerical properties of the conventional least squares estimator.
NASA Astrophysics Data System (ADS)
Vadas, S.; Makela, J. J.; Fisher, D. J.
2014-12-01
In this poster, we discuss new solutions which describe the excitation of acoustic gravity waves from a moving surface ocean wave. We then describe a new method by which to ray trace the gravity waves into the thermosphere. We show that the ray traced-solutions equal theexact Fourier-Laplace solutions in the limit that the winds are zero,the temperature is constant, and thermospheric dissipation is turned off. We then apply these solutions to the gravity waves excited by a moving ocean wave using realisitic wind, temperature and thermospheric dissipation. Finally, we apply these results to a recently-observedtsunami.
NASA Astrophysics Data System (ADS)
Minato, Atsushi; Sugimoto, Nobuo; Bleier, Zvi; Hunter, George C.; Paul, James
1995-08-01
A 50-cm diameter hollow cube-corner retroreflector for a space application was tested with a 60-cm interferometer. To separate the effect of sag due to gravity, the interferograms were taken at six rotational positions, with the retroreflector mounted horizontally. The zero-gravity dihedral angles and the effect of sag were estimated from the interferograms.
NSDL National Science Digital Library
National Science Teachers Association (NSTA)
2007-03-21
The Gravity and Orbits SciPack explores concepts related to Earth's universal gravitation and how gravity affects the universe around us. The focus is on Standards and Benchmarks related to universal gravitation including variables that influence the amount of gravitational force and how gravity governs the motion of the solar system.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:? Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. ? Access to one-on-one support via e-mail to content "Wizards".? Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Gravity and Orbits: Universal Gravitation? Identify gravity as an attractive force associated with all objects, including less intuitive examples (such as soda cans and pencils).? Recognize some examples of phenomena that are the result of Earth's gravity and objects and structures in the universe in general.? Reject the idea that Earth's gravity is an effect of air pushing down toward the surface.? Recognize that gravitational force does not require air (or any other substance) as a medium to act.? Describe gravitational force as a mutual attraction, rather than as one object pulling on another.Gravity and Orbits: Gravitational Force? Identify variables that affect the strength of the gravitational force acting between any two objects.? Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.? Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.? Provide a quantitative description of the relationship between distance and gravitational force. ? Provide a qualitative description of the inverse square relationship.? Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored. Gravity and Orbits: Orbits? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.
Zero-order bows in radially inhomogeneous spheres: direct and inverse problems.
Adam, John A
2011-10-01
Zero-order ray paths are examined in radially inhomogeneous spheres with differentiable refractive index profiles. It is demonstrated that zero-order and sometimes twin zero-order bows can exist when the gradient of refractive index is sufficiently negative. Abel inversion is used to "recover" the refractive index profiles; it is therefore possible in principle to specify the nature and type of bows and determine the refractive index profile that induces them. This may be of interest in the field of rainbow refractometry and optical fiber studies. This ray-theoretic analysis has direct similarities with the phenomenon of "orbiting" and other phenomena in scattering theory and also in seismological, surface gravity wave, and gravitational "lensing" studies. For completeness these topics are briefly discussed in the appendixes; they may also be of pedagogic interest. PMID:22016245
Exactly Soluble Sector of Quantum Gravity
Joy Christian
2005-11-07
Cartan's spacetime reformulation of the Newtonian theory of gravity is a generally-covariant Galilean-relativistic limit-form of Einstein's theory of gravity known as the Newton-Cartan theory. According to this theory, space is flat, time is absolute with instantaneous causal influences, and the degenerate `metric' structure of spacetime remains fixed with two mutually orthogonal non-dynamical metrics, one spatial and the other temporal. The spacetime according to this theory is, nevertheless, curved, duly respecting the principle of equivalence, and the non-metric gravitational connection-field is dynamical in the sense that it is determined by matter distributions. Here, this generally-covariant but Galilean-relativistic theory of gravity with a possible non-zero cosmological constant, viewed as a parameterized gauge theory of a gravitational vector-potential minimally coupled to a complex Schroedinger-field (bosonic or fermionic), is successfully cast -- for the first time -- into a manifestly covariant Lagrangian form. Then, exploiting the fact that Newton-Cartan spacetime is intrinsically globally-hyperbolic with a fixed causal structure, the theory is recast both into a constraint-free Hamiltonian form in 3+1-dimensions and into a manifestly covariant reduced phase-space form with non-degenerate symplectic structure in 4-dimensions. Next, this Newton-Cartan-Schroedinger system is non-perturbatively quantized using the standard C*-algebraic technique combined with the geometric procedure of manifestly covariant phase-space quantization. The ensuing unitary quantum field theory of Newtonian gravity coupled to Galilean-relativistic matter is not only generally-covariant, but also exactly soluble.
Landau levels and Riemann zeros
German Sierra; Paul K. Townsend
2008-09-22
The number $N(E)$ of complex zeros of the Riemann zeta function with positive imaginary part less than $E$ is the sum of a `smooth' function $\\bar N(E)$ and a `fluctuation'. Berry and Keating have shown that the asymptotic expansion of $\\bar N(E)$ counts states of positive energy less than $E$ in a `regularized' semi-classical model with classical Hamiltonian $H=xp$. For a different regularization, Connes has shown that it counts states `missing' from a continuum. Here we show how the `absorption spectrum' model of Connes emerges as the lowest Landau level limit of a specific quantum mechanical model for a charged particle on a planar surface in an electric potential and uniform magnetic field. We suggest a role for the higher Landau levels in the fluctuation part of $N(E)$.
Wintercorn, S.J.; /Fermilab
1986-04-07
The system pumping speed was calculated by taking the reciprocal of the sum of the reciprocal pump speed and the reciprocal line conductances. The conductances of the pipe were calculated from the following formulas taken from the Varian vacuum manual. This report updates the original to reflect the pumping curves and basic vacuum system characteristics for the purchased components and installed piping of the D-Zero vacuum system. The system consists of two Edward's E2M275 two stage mechanical pumps, a Leybold-Heraeus WSU2000 Blower and three Varian 4' diffusion pumps (one for each cryostat). Individual pump and system pumping speed curves and a diagram of the system is included.
A study of two-phase flow in a reduced gravity environment
NASA Technical Reports Server (NTRS)
Hill, D.; Downing, Robert S.
1987-01-01
A test loop was designed and fabricated for observing and measuring pressure drops of two-phase flow in reduced gravity. The portable flow test loop was then tested aboard the NASA-JSC KC135 reduced gravity aircraft. The test loop employed the Sundstrand Two-Phase Thermal Management System (TPTMS) concept which was specially fitted with a clear two-phase return line and condenser cover for flow observation. A two-phase (liquid/vapor) mixture was produced by pumping nearly saturated liquid through an evaporator and adding heat via electric heaters. The quality of the two-phase flow was varied by changing the evaporator heat load. The test loop was operated on the ground before and after the KC135 flight tests to create a one-gravity data base. The ground testing included all the test points run during the reduced gravity testing. Two days of reduced gravity tests aboard the KC135 were performed. During the flight tests, reduced-gravity, one-gravity, and nearly two-gravity accelerations were experienced. Data was taken during the entire flight which provided flow regime and pressure drop data for the three operating conditions. The test results show that two-phase pressure drops and flow regimes can be accurately predicted in zero-gravity.
The influence of simulated low-gravity environments on growth, development and metabolism of plants.
Dedolph, R R
1967-01-01
Low-gravity environments may be simulated through appropriate horizontal clinostat rotation. This simulation is accomplished through a biological nullification of the directional component of gravitational force. Measuring biologically effective gravity force by organ response, it is readily demonstrated that biologically active gravitational force may be treated as a two-dimensional vector. Though the magnitude dimension of this vector remains virtually constant anywhere on earth, the biologically effective direction dimension may be quantitatively altered by clinostat rotation, provided appropriate angular velocities and angles of inclination of clinostat axes are employed. Using oat seedlings, a rotation rate of 2 rpm, and a horizontal axis clinostat, a 'zero g' environment may be simulated. This simulated 'zero g' condition is attested by the inability of plants to perceive unidirectional gravitational force of sufficient magnitude to elicit directional growth. Under such conditions, plants will grow in the direction imparted by the initial orientation of the plants in the system. Geotropic curvature responses to subsequent geostimulation are, however, greater in seedlings grown under these conditions, nullifying the direction dimension of gravitational force, than in seedlings grown with rotation but with normal unidirectional gravity loads. Root growth under simulated 'zero' gravity conditions is likewise enhanced as compared to plants grown with rotation but normal unidirectional gravity. These differences in magnitude of growth and response to subsequent geostimulation are inexplicable on bases of modified auxin economy or production. Respiration rates are, however, materially enhanced by the simulated 'zero g' environments. This enhancement of respiration, as well as growth, quantitatively diminishes as the unidirectional gravity load is increased. These results imply that the primary effect of low-gravity environments is likely that of modifying the magnitude of respiratory metabolism. Such a modification is partly or wholly explicable on a basis of a modified distribution pattern of metabolically active particulate cell inclusions. PMID:11973847
Paul B. Slater
2007-03-26
Wu and Sprung (Phys. Rev. E 48, 2595 (1993)) reproduced the first 500 nontrivial Riemann zeros, using a one-dimensional local potential model. They concluded -- and similarly van Zyl and Hutchinson (Phys. Rev. E 67, 066211 (2003)) -- that the potential possesses a fractal structure of dimension d=3/2. We model the nonsmooth fluctuating part of the potential by the alternating-sign sine series fractal of Berry and Lewis A(x,g). Setting d=3/2, we estimate the frequency parameter (gamma), plus an overall scaling parameter (sigma) we introduce. We search for that pair of parameters (gamma,sigma) which minimizes the least-squares fit S_{n}(gamma,sigma) of the lowest n eigenvalues -- obtained by solving the one-dimensional stationary (non-fractal) Schrodinger equation with the trial potential (smooth plus nonsmooth parts) -- to the lowest n Riemann zeros for n =25. For the additional cases we study, n=50 and 75, we simply set sigma=1. The fits obtained are compared to those gotten by using just the smooth part of the Wu-Sprung potential without any fractal supplementation. Some limited improvement -- 5.7261 vs. 6.39207 (n=25), 11.2672 vs. 11.7002 (n=50) and 16.3119 vs. 16.6809 (n=75) -- is found in our (non-optimized, computationally-bound) search procedures. The improvements are relatively strong in the vicinities of gamma=3 and (its square) 9. Further, we extend the Wu-Sprung semiclassical framework to include higher-order corrections from the Riemann-von Mangoldt formula (beyond the leading, dominant term) into the smooth potential.
Maglev Facility for Simulating Variable Gravity
NASA Technical Reports Server (NTRS)
Liu, Yuanming; Strayer, Donald M.; Israelsson, Ulf E.
2010-01-01
An improved magnetic levitation apparatus ("Maglev Facility") has been built for use in experiments in which there are requirements to impose variable gravity (including zero gravity) in order to assess the effects of gravity or the absence thereof on physical and physiological processes. The apparatus is expected to be especially useful for experiments on the effects of gravity on convection, boiling, and heat transfer in fluids and for experiments on mice to gain understanding of bone loss induced in human astronauts by prolonged exposure to reduced gravity in space flight. The maglev principle employed by the apparatus is well established. Diamagnetic cryogenic fluids such as liquid helium have been magnetically levitated for studying their phase transitions and critical behaviors. Biological entities consist mostly of diamagnetic molecules (e.g., water molecules) and thus can be levitated by use of sufficiently strong magnetic fields having sufficiently strong vertical gradients. The heart of the present maglev apparatus is a vertically oriented superconducting solenoid electromagnet (see figure) that generates a static magnetic field of about 16 T with a vertical gradient sufficient for levitation of water in normal Earth gravity. The electromagnet is enclosed in a Dewar flask having a volume of 100 L that contains liquid helium to maintain superconductivity. The Dewar flask features a 66-mm-diameter warm bore, lying within the bore of the magnet, wherein experiments can be performed at room temperature. The warm bore is accessible from its top and bottom ends. The superconducting electromagnet is run in the persistent mode, in which the supercurrent and the magnetic field can be maintained for weeks with little decay, making this apparatus extremely cost and energy efficient to operate. In addition to water, this apparatus can levitate several common fluids: liquid hydrogen, liquid oxygen, methane, ammonia, sodium, and lithium, all of which are useful, variously, as rocket fuels or as working fluids for heat transfer devices. A drop of water 45 mm in diameter and a small laboratory mouse have been levitated in this apparatus.
NASA Astrophysics Data System (ADS)
Herdeiro, Carlos; Hirano, Shinji; Sato, Yuki
2011-12-01
n-DBI gravity is a gravitational theory introduced in [C. Herdeiro and S. Hirano, arXiv:1109.1468.], motivated by Dirac-Born-Infeld type conformal scalar theory and designed to yield noneternal inflation spontaneously. It contains a foliation structure provided by an everywhere timelike vector field n, which couples to the gravitational sector of the theory, but decouples in the small curvature limit. We show that any solution of Einstein gravity with a particular curvature property is a solution of n-DBI gravity. Among them is a class of geometries isometric to a Reissner-Nordström-(anti)-de Sitter black hole, which is obtained within the spherically symmetric solutions of n-DBI gravity minimally coupled to the Maxwell field. These solutions have, however, two distinct features from their Einstein gravity counterparts: (1) the cosmological constant appears as an integration constant and can be positive, negative, or vanishing, making it a variable quantity of the theory; and (2) there is a nonuniqueness of solutions with the same total mass, charge, and effective cosmological constant. Such inequivalent solutions cannot be mapped to each other by a foliation preserving diffeomorphism. Physically they are distinguished by the expansion and shear of the congruence tangent to n, which define scalar invariants on each leaf of the foliation.
NASA Technical Reports Server (NTRS)
Morey-Holton, Emily R.
1996-01-01
Gravity has been the most constant environmental factor throughout the evolution of biological species on Earth. Organisms are rarely exposed to other gravity levels, either increased or decreased, for prolonged periods. Thus, evolution in a constant 1G field has historically prevented us from appreciating the potential biological consequences of a multi-G universe. To answer the question 'Can terrestrial life be sustained and thrive beyond our planet?' we need to understand the importance of gravity on living systems, and we need to develop a multi-G, rather than a 1G, mentality. The science of gravitational biology took a giant step with the advent of the space program, which provided the first opportunity to examine living organisms in gravity environments lower than could be sustained on Earth. Previously, virtually nothing was known about the effects of extremely low gravity on living organisms, and most of the initial expectations were proven wrong. All species that have flown in space survive in microgravity, although no higher organism has ever completed a life cycle in space. It has been found, however, that many systems change, transiently or permanently, as a result of prolonged exposure to microgravity.
1/R gravity and Scalar-Tensor Gravity
Takeshi Chiba
2003-09-09
We point out that extended gravity theories, the Lagrangian of which is an arbitrary function of scalar curvature $R$, are equivalent to a class of the scalar tensor theories of gravity. The corresponding gravity theory is $\\omega=0$ Brans-Dicke gravity with a potential for the Brans-Dicke scalar field, which is not compatible with solar system experiments if the field is very light: the case when such modifications are important recently.
On the no-gravity limit of gravity
J. Kowalski-Glikman; M. Szczachor
2012-12-21
We argue that Relative Locality may arise in the no gravity $G\\rightarrow0$ limit of gravity. In this limit gravity becomes a topological field theory of the BF type that, after coupling to particles, may effectively deform its dynamics. We briefly discuss another no gravity limit with a self dual ground state as well as the topological ultra strong $G\\rightarrow\\infty$ one.
Zero-knowledge against quantum attacks
John Watrous
2005-11-03
This paper proves that several interactive proof systems are zero-knowledge against quantum attacks. This includes a few well-known classical zero-knowledge proof systems as well as quantum interactive proof systems for the complexity class HVQSZK, which comprises all problems having "honest verifier" quantum statistical zero-knowledge proofs. It is also proved that zero-knowledge proofs for every language in NP exist that are secure against quantum attacks, assuming the existence of quantum computationally concealing commitment schemes. Previously no non-trivial proof systems were known to be zero-knowledge against quantum attacks, except in restricted settings such as the honest-verifier and common reference string models. This paper therefore establishes for the first time that true zero-knowledge is indeed possible in the presence of quantum information and computation.
Brans-Dicke gravity theory from topological gravity
NASA Astrophysics Data System (ADS)
Inostroza, C.; Salazar, A.; Salgado, P.
2014-06-01
We consider a model that suggests a mechanism by which the four dimensional Brans-Dicke gravity theory may emerge from the topological gravity action. To achieve this goal, both the Lie algebra and the symmetric invariant tensor that define the topological gravity Lagrangian are constructed by means of the Lie algebra S-expansion procedure with an appropriate abelian semigroup S.
Inflation without quantum gravity
NASA Astrophysics Data System (ADS)
Markkanen, Tommi; Räsänen, Syksy; Wahlman, Pyry
2015-04-01
It is sometimes argued that observation of tensor modes from inflation would provide the first evidence for quantum gravity. However, in the usual inflationary formalism, also the scalar modes involve quantized metric perturbations. We consider the issue in a semiclassical setup in which only matter is quantized, and spacetime is classical. We assume that the state collapses on a spacelike hypersurface and find that the spectrum of scalar perturbations depends on the hypersurface. For reasonable choices, we can recover the usual inflationary predictions for scalar perturbations in minimally coupled single-field models. In models where nonminimal coupling to gravity is important and the field value is sub-Planckian, we do not get a nearly scale-invariant spectrum of scalar perturbations. As gravitational waves are only produced at second order, the tensor-to-scalar ratio is negligible. We conclude that detection of inflationary gravitational waves would indeed be needed to have observational evidence of quantization of gravity.
Macroscopic quantization of gravity
M. Y. Amin
2010-01-09
The moon is receding from earth at an average rate of 3.8 cm/yr [6][7][9][12].This anomaly cannot be attributed to the well-known tidal exchange of angular momentum between earth and moon [8]. A secular change in the astronomical unit AU is definitely a concern, it is reportedly increasing by about 15 cm/yr [9][10], in this letter; the concept of macroscopic quantization of gravity is introduced to account for these anomalies on theoretical basis. Interestingly, it was found useful in measuring the speed of gravity! What is more interesting is the fact that this concept is based on solid well known classical physics with no modifications to any standard model. It was found that the speed of gravity cg is in the range 10^4 c < cg < 10^5 c.
NSDL National Science Digital Library
National Science Teachers Association (NSTA)
2006-11-01
This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.
Leonardo Modesto
2013-05-29
We hereby present a class of multidimensional higher derivative theories of gravity that realizes an ultraviolet completion of Einstein general relativity. This class is marked by a "non-polynomal" entire function (form factor), which averts extra degrees of freedom (including ghosts) and improves the high energy behavior of the loop amplitudes. By power counting arguments, it is proved that the theory is super-renormalizable in any dimension, i.e. only one-loop divergences survive. Furthermore, in odd dimensions there are no counter terms for pure gravity and the theory turns out to be "finite." Finally, considering the infinite tower of massive states coming from dimensional reduction, quantum gravity is finite in even dimension as well.
V. N. Borodikhin
2011-04-14
We proposed a gravitation theory based on an analogy with electrodynamics on the basis of a vector field. For the first time, to calculate the basic gravitational effects in the framework of a vector theory of gravity, we use a Lagrangian written with gravitational radiation neglected and generalized to the case of ultra-relativistic speeds. This allows us to accurately calculate the values of all three major gravity experiments: the values of the perihelion shift of Mercury, the light deflection angle in the gravity field of the Sun and the value of radar echo delay. The calculated values coincide with the observed ones. It is shown that, in this theory, there exists a model of an expanding Universe.
Understanding Something About Nothing: Radiation Zeros
Robert W. Brown
1995-06-02
Radiation symmetry is briefly reviewed, along with its historical, experimental, computational, and theoretical relevance. A sketch of the proof of a theorem for radiation zeros is used to highlight the connection between gauge-boson couplings and Poincare transformations. It is emphasized that while mostly bad things happen to good zeros, the weak-boson self-couplings continue to be intimately tied to the best examples of exact or approximate zeros.
NASA Technical Reports Server (NTRS)
1943-01-01
Mitsubishi A6M2 'Zero': Captured at Akutan Island, Alaska, in August 1942, this Mitsubishi A6M2 fighter was the first 'Zero' to fall intact into Allied hands during WW II. After limited flying on the West Coast, the 'Zero' arrived at Langley for installation of test equipment prior to in-depth flight testing by the Navy at Patuxent River, Maryland.
Random complex zeroes, II. Perturbed lattice
Mikhail Sodin; Boris Tsirelson
2006-01-01
We show that the flat chaotic analytic zero points (i.e. zeroes of a random entire function\\u000a $$\\\\psi (z) = \\\\sum {_{k = 0}^\\\\infty \\\\zeta } k\\\\frac{{z^k }}{{\\\\sqrt {k!} }}$$\\u000a where ?0, ?1, are independent standard complex-valued Gaussian variables) can be regarded as a random perturbation of a lattice in the\\u000a plane. The distribution of the distances between the zeroes
Zero modes for the giant magnon
J. A. Minahan
2007-01-22
We explicitly construct the eight fermion zero mode solutions for the Hofman-Maldacena giant magnon. The solutions are naturally gauge fixed under the \\kappa-symmetry. Substituting the solutions back into the Lagrangian leads to a simple expression that can be quantized directly. We also show how to construct the SU(2|2)\\times SU(2|2) superalgebra from these zero modes. For completeness we also find the four bosonic zero mode solutions.
The complexity of perfect zero-knowledge
L. Fortnow
1987-01-01
A Perfect Zero-Knowledge interactive proof system convinces a verifier that a string is in a language without revealing any additional knowledge in an information-theoretic sense. We show that for any language that has a perfect zero-knowledge proof system, its complement has a short interactive protocol. This result implies that there are not any perfect zero-knowledge protocols for NP-complete languages unless
Zero Knowledge and Soundness Are Symmetric
Shien Jin Ong; Salil P. Vadhan
2007-01-01
We give a complexity-theoretic characterization of the class of problems in NP having zero-knowledge argument systems. This char- acterization is symmetric in its treatment of the zero knowledge and the soundness conditions, and thus we deduce that the class of prob- lems in NP \\\\ coNP having zero-knowledge arguments is closed under complement. Furthermore, we show that a problem in
Complex spectrally arbitrary zerononzero patterns
J. J. McDonald; A. A. Yielding
2012-01-01
In this article, we highlight interesting properties of complex spectrally arbitrary zerononzero patterns. In particular, we investigate irreducible complex spectrally arbitrary zerononzero patterns for which all Jacobians are zero at every nilpotent realization. We also study complex spectrally arbitrary patterns whose corresponding directed graph does not contain a two-cycle. Lastly, we provide a complete list of all 3?×?3 and 4?×?4
Complex spectrally arbitrary zerononzero patterns
J. J. McDonald; A. A. Yielding
2011-01-01
In this article, we highlight interesting properties of complex spectrally arbitrary zerononzero patterns. In particular, we investigate irreducible complex spectrally arbitrary zerononzero patterns for which all Jacobians are zero at every nilpotent realization. We also study complex spectrally arbitrary patterns whose corresponding directed graph does not contain a two-cycle. Lastly, we provide a complete list of all 3?×?3 and 4?×?4
External Resource: Gravity Assist Simulator
NSDL National Science Digital Library
1900-01-01
A Messenger Education site to explore gravity assist maneuvers, interaction with gravity, and the idea of a collision, to understand the effects of that interaction. Students explore the simulated encounters of spacecraft and planets to answer the questio
NASA Astrophysics Data System (ADS)
Maartens, Roy; Koyama, Kazuya
2010-09-01
The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+d-dimensional spacetime (the "bulk"), with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity leaks into the bulk, behaving in a truly higher-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting and potentially testable implications for high-energy astrophysics, black holes, and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review analyzes the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models. We also cover the simplest brane-world models in which 4-dimensional gravity on the brane is modified at low energies - the 5-dimensional Dvali-Gabadadze-Porrati models. Then we discuss co-dimension two branes in 6-dimensional models.
NASA Net Zero Energy Buildings Roadmap
Pless, S.; Scheib, J.; Torcellini, P.; Hendron, B.; Slovensky, M.
2014-10-01
In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategic approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.
Nonlinear magnetohydrodynamics from gravity
NASA Astrophysics Data System (ADS)
Hansen, James; Kraus, Per
2009-04-01
We apply the recently established connection between nonlinear fluid dynamics and AdS gravity to the case of the dyonic black brane in AdS4. This yields the equations of fluid dynamics for a 2+1 dimensional charged fluid in a background magnetic field. We construct the gravity solution to second order in the derivative expansion. From this we find the fluid dynamical stress tensor and charge current to second and third order in derivatives respectively, along with values for the associated transport coefficients.
Asymptotically Safe Lorentzian Gravity
Manrique, Elisa; Rechenberger, Stefan; Saueressig, Frank [Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, D-55099 Mainz (Germany)
2011-06-24
The gravitational asymptotic safety program strives for a consistent and predictive quantum theory of gravity based on a nontrivial ultraviolet fixed point of the renormalization group (RG) flow. We investigate this scenario by employing a novel functional renormalization group equation which takes the causal structure of space-time into account and connects the RG flows for Euclidean and Lorentzian signature by a Wick rotation. Within the Einstein-Hilbert approximation, the {beta} functions of both signatures exhibit ultraviolet fixed points in agreement with asymptotic safety. Surprisingly, the two fixed points have strikingly similar characteristics, suggesting that Euclidean and Lorentzian quantum gravity belong to the same universality class at high energies.
Consistency of Semiclassical Gravity
D. Giulini; C. Kiefer
1994-09-08
We discuss some subtleties which arise in the semiclassical approximation to quantum gravity. We show that integrability conditions prevent the existence of Tomonaga-Schwinger time functions on the space of three-metrics but admit them on superspace. The concept of semiclassical time is carefully examined. We point out that central charges in the matter sector spoil the consistency of the semiclassical approximation unless the full quantum theory of gravity and matter is anomaly-free. We finally discuss consequences of these considerations for quantum field theory in flat spacetime, but with arbitrary foliations.
Nonlinear Magnetohydrodynamics from Gravity
James Hansen; Per Kraus
2009-01-08
We apply the recently established connection between nonlinear fluid dynamics and AdS gravity to the case of the dyonic black brane in AdS_4. This yields the equations of fluid dynamics for a 2+1 dimensional charged fluid in a background magnetic field. We construct the gravity solution to second order in the derivative expansion. From this we find the fluid dynamical stress tensor and charge current to second and third order in derivatives respectively, along with values for the associated transport coefficients.
NASA Technical Reports Server (NTRS)
Mather, R. S.
1973-01-01
Procedures for obtaining position from surface gravity observations are reviewed and their relevance assessed in the context of the application of modern geodetic techniques to programs of Earth and ocean physics. Solutions based on the use of surface layer techniques, the discrete value approach, and the development from Green's theorem are stated in summary, the latter being extended to order e cubed in the height anomaly. The representation of the surface gravity field which is required in order that this accuracy may be achieved is discussed. Interim techniques which could be used in the absence of such a representation are also outlined.
Generalized Gravity and a Ghost
Takeshi Chiba
2005-03-22
We show that generalized gravity theories involving the curvature invariants of the Ricci tensor and the Riemann tensor as well as the Ricci scalar are equivalent to multi- scalar-tensor gravities with four derivatives terms. By expanding the action around a vacuum spacetime, the action is reduced to that of the Einstein gravity with four derivative terms, and consequently there appears a massive spin-2 ghost in such generalized gravity theories in addition to a massive spin-0 field.
Introduction to Loop Quantum Gravity
Simone Mercuri
2010-01-08
The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.
Skewness in the cosmic microwave background anisotropy from an inflationary gravity wave background
Souradeep, Tarun
photons off the metric perturbations. We provide a simple and elegant formalism for deriving the CMB. The detection of tiny anisotro pies in the CMB by the Cosmic Background Explorer ~COBE! Differential Microwave to the superadia batic amplification of zeropoint quantum fluctuations occur ring during inflation. As gravity
A unified approach to ZMP and gravity center control in biped dynamic stable walking
K. Sorao; T. Murakami; K. Ohnishi
1997-01-01
Summary form only given. In this paper, to realize dynamic stable walking, a novel control strategy is formulated, which is based on both the centre of gravity (COG) and the zero moment point (ZMP) of the biped supporting leg control. This control algorithm involves the following two stages: 1) trajectory generation of the ZMP for the realization of the arbitrary
Effects of Topology Change in Brans-Dicke Theory of Gravity
Hongsu Kim
1991-01-01
Effects of topology change on low energy physics in the framework of Brans-Dicke theory of gravity is studied especially associated with the wormhole physics solution to the cosmological constant problem. It is shown that wormhole effects drive the value of observable effective cosmological constant to zero at later universes whereas to an enormous constant value large enough for the occurrence
Linearized Torsion Waves in a Tensor-Tensor Theory of Gravity
Chih-Hung Wang
2007-12-12
We investigate a linearized tensor-tensor theory of gravity with torsion and a perturbed torsion wave solution is discovered in background Minkowski spacetime with zero torsion. Furthermore, gauge transformations of any perturbed tensor field are derived in general background non-Riemannian geometries. By calculating autoparallel deviations, both longitudinal and transverse polarizations of the torsion wave are discovered.
Loop quantum gravity and observations
A. Barrau; J. Grain
2014-10-07
Quantum gravity has long been thought to be completely decoupled from experiments or observations. Although it is true that smoking guns are still missing, there are now serious hopes that quantum gravity phenomena might be tested. We review here some possible ways to observe loop quantum gravity effects either in the framework of cosmology or in astroparticle physics.
Gravity Recovery and Climate Experiment
NSDL National Science Digital Library
The Gravity Recovery and Climate Experiment (GRACE) mission uses twin satellites to make detailed measurements of Earth's gravity field. GRACE materials include a description of the mission, research projects, and personnel. There are also links to news articles, publications, datasets, and software tools for processing gravity data.
6, 19532001, 2006 Imaging gravity
Boyer, Edmond
ACPD 6, 19532001, 2006 Imaging gravity waves in lower stratospheric AMSU-A radiances S. D under a Creative Commons License. Atmospheric Chemistry and Physics Discussions Imaging gravity waves.eckermann@nrl.navy.mil) 1953 #12;ACPD 6, 19532001, 2006 Imaging gravity waves in lower stratospheric AMSU-A radiances S. D
CFT, Integrable Models Liouville Gravity
Fominov, Yakov
CFT, Integrable Models And Liouville Gravity Chernogolovka 2009 Sunday June 28, 2009. Conference as one of components of their L, A pairs. #12;CFT, Integrable Models And Liouville Gravity Chernogolovka Gravity Chernogolovka, 2009 Tuesday June 30, 2009. CONFERENCE HALL 09:3010:10 Herman Boos (Wuppertal
5, 1102911054, 2005 Convective gravity
Paris-Sud XI, Université de
ACPD 5, 1102911054, 2005 Convective gravity waves at mid-latitudes Y. G. Choi et al. Title Page Discussions Wind-profiler observations of gravity waves produced by convection at mid-latitudes Y. G. Choi111054, 2005 Convective gravity waves at mid-latitudes Y. G. Choi et al. Title Page Abstract Introduction
Introduction Basics of gravity theory
Visser, Matt
Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion;Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion and Conclusions Is there a way out? A high-energy theory of gravity? Fact GR is a classical theory what happens in the Plank
Non-anticommutative quantum gravity
NASA Astrophysics Data System (ADS)
Moffat, J. W.
2015-06-01
A calculation of the one loop gravitational self-energy graph in non-anticommutative quantum gravity reveals that graviton loops are damped by internal momentum dependent factors in the modified propagator and the vertex functions. The non-anticommutative quantum gravity perturbation theory is finite for matter-free gravity and for matter interactions.
Does Paramecium sense gravity?
Mogami, Y; Ishii, J; Baba, S A
1995-03-01
In order to get an insight into the cellular mechanisms for the integration of the effects of gravity, we investigated the gravitactic behaviour in Paramecium. There are two main categories for the model of the mechanism of gravitaxis; one is derived on the basis of the mechanistic properties of the cell (physical model) and the other of the physiological properties including cellular gravireception (physiological model). In this review article, we criticized the physical models and introduced a new physiological model. Physical models postulated so far can be divided into two; one explaining the negative gravitactic orientation of the cell in terms of the static torque generated by the structural properties of the cell (gravity-buoyancy model by Verworn, 1889 and drag-gravity model by Roberts, 1970), and the other explaining it in terms of the dynamic torque generated by the helical swimming of the cell (propulsion-gravity model by Winet and Jahn, 1974 and lifting-force model by Nowakowska and Grebecki, 1977). Among those we excluded the possibility of dynamic-torque models because of their incorrect theoretical assumptions. According to the passive orientation of Ni(2+)-immobilized cells, the physical effect of the static torque should be inevitable for the gravitactic orientation. Downward orientation of the immobilized cells in the course of floating up in the hyper-density medium demonstrated the gravitactic orientation is not resulted by the nonuniform distribution of cellular mass (gravity-buoyancy model) but by the fore-aft asymmetry of the cell (drag-gravity model). A new model explaining the gravitactic behaviour is derived on the basis of the cellular gravity sensation through mechanoreceptor channels of the cell membrane. Paramecium is known to have depolarizing receptor channels in the anterior and hyperpolarizing receptors in the posterior of the cell. The uneven distribution of the receptor may lead to the bidirectional changes of the membrane potential by the selective deformation of the anterior and posterior cell membrane responding to the orientation of the cell in the gravity field; i.e. negative- and positive-going shift of the potential due to the upward and downward orientation, respectively. The orientation dependent changes in membrane potential with respect to gravity, in combination with the close coupling of the membrane potential and the ciliary locomotor activity, may allow the changes in swimming direction along with those in the helical nature of the swimming path; upward shift of axis of helix by decreasing the pitch angle due to hyperpolarization in the upward-orienting cell, and also the upward shift by increasing the pitch angle due to depolarization in the downward-orienting cell. Computer simulation of the model demonstrated that the cell can swim upward along the "super-helical" trajectory consisting of a small helix winding helically an axis parallel to the gravity vector, after which the model was named as "Super-helix model". Three-dimensional recording of the trajectories of the swimming cells demonstrated that about a quarter of the cell population drew super-helical trajectory under the unbounded, thermal convection-free conditions. In addition, quantitative analysis of the orientation rate of the swimming cell indicated that gravity-dependent orientation of the swimming trajectory could not be explained solely by the physical static torque but complementarily by the physiological mechanism as proposed in the super-helix model. PMID:11541872
Even-dimensional topological gravity from Chern-Simons gravity
Nelson Merino; Alfredo Perez; Patricio Salgado
2009-10-08
It is shown that the topological action for gravity in 2n-dimensions can be obtained from the 2n+1-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a 2n+1-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field $\\phi^{a}$, which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).
From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity
Kristina Giesel; Hanno Sahlmann
2013-01-02
We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity.
Induced Gravity in the Short Range
C. P. Kouropoulos
2001-08-09
We consider a pair of harmonic oscillators in two or three dimensions of space coupled by the standard electrodynamic forces : the Coulomb, the Lorentz and the electrokinetic forces. The addition of the Lorentz force is mainly felt in the short range and suppresses the radial correlated oscillating mode of such coupled oscillators. This imposes constraints on the system that make the two transverse modes degenerate. As a result, an 1/r antigravitational interaction now appears in the surviving anticorrelated radial zero-mode, which does not allow coherent states to form. As gravitation can only emerge from coherent modes, it can no longer be transitive. Matter in high densities would thus tend to increase its disorder, decouple from its own gravity, from the ordering far infrared Machian background that coheres its rest energy and would become intrinsically unstable. The highly energetic jets from galactic nuclei could be the consequence.
Hardware development for Gravity Probe-B
NASA Technical Reports Server (NTRS)
Bardas, D.; Cheung, W. S.; Gill, D.; Hacker, R.; Keiser, G. M.
1986-01-01
Gravity Probe-B (GP-B), also known as the Stanford Relativity Gyroscope Experiment, will test two fundamental predictions of Einstein's General Theory of Relativity by precise measurement of the precessions of nearly perfect gyroscopes in earth orbit. This endeavor embodies state-of-the-art technologies in many fields, including gyroscope fabrication and readout, cryogenics, superconductivity, magnetic shielding, precision optics and alignment methods, and satellite control systems. These technologies are necessary to enable measurement of the predicted precession rates to the milliarcsecond/year level, and to reduce to 'near zero' all non-General Relativistic torques on the gyroscopes. This paper provides a brief overview of the experiment followed by descriptions of several specific hardware items with highlights on progress to date and plans for future development and tests.
Gravity localization in sine-Gordon braneworlds
W. T. Cruz; R. V. Maluf; L. J. S. Sousa; C. A. S. Almeida
2014-12-29
In this work we study two types of five-dimensional braneworld models given by sine-Gordon potentials. In both scenarios, the thick brane is generated by a real scalar field coupled to gravity. We focus our investigation on the localization of graviton field and the behaviour of the massive spectrum. In particular, we analyse the localization of massive modes by means of a relative probability method in a Quantum Mechanics context. Initially, considering a scalar field sine-Gordon potential, we find a resonance to the graviton at zero mode. However, when we consider a double sine-Gordon potential, the brane structure is changed allowing the existence of massless and massive resonant states. The new results show how the existence of an internal structure can aid in the emergence of massive resonant modes on the brane.
NASA Technical Reports Server (NTRS)
Bowin, C. O.
1976-01-01
Lunar gravitational properties were analyzed along with the development of flat moon and curved moon computer models. Gravity anomalies and mascons were given particular attention. Geophysical and geological considerations were included, and comparisons were made between the gravitional fields of the Earth, Mars, and the Moon.
Semiclassical unimodular gravity
Fiol, Bartomeu; Garriga, Jaume, E-mail: bfiol@ub.edu, E-mail: jaume.garriga@ub.edu [Departament de Física Fonamental i, Institut de Cičncies del Cosmos, Universitat de Barcelona, Martí i Franqučs 1, 08028 Barcelona (Spain)
2010-08-01
Classically, unimodular gravity is known to be equivalent to General Relativity (GR), except for the fact that the effective cosmological constant ? has the status of an integration constant. Here, we explore various formulations of unimodular gravity beyond the classical limit. We first consider the non-generally covariant action formulation in which the determinant of the metric is held fixed to unity. We argue that the corresponding quantum theory is also equivalent to General Relativity for localized perturbative processes which take place in generic backgrounds of infinite volume (such as asymptotically flat spacetimes). Next, using the same action, we calculate semiclassical non-perturbative quantities, which we expect will be dominated by Euclidean instanton solutions. We derive the entropy/area ratio for cosmological and black hole horizons, finding agreement with GR for solutions in backgrounds of infinite volume, but disagreement for backgrounds with finite volume. In deriving the above results, the path integral is taken over histories with fixed 4-volume. We point out that the results are different if we allow the 4-volume of the different histories to vary over a continuum range. In this ''generalized'' version of unimodular gravity, one recovers the full set of Einstein's equations in the classical limit, including the trace, so ? is no longer an integration constant. Finally, we consider the generally covariant theory due to Henneaux and Teitelboim, which is classically equivalent to unimodular gravity. In this case, the standard semiclassical GR results are recovered provided that the boundary term in the Euclidean action is chosen appropriately.
NASA Astrophysics Data System (ADS)
Rovelli, Carlo
1998-04-01
The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. The research in loop quantum gravity forms today a vast area, ranging from mathematical foundations to physical applications. Among the most significative results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume; which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, overcompleteness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. I will provide an overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity.
NASA Astrophysics Data System (ADS)
Rovelli, Carlo
1998-01-01
The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
Quantum Gravity and Turbulence
Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze
2010-05-18
We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.
Delbourgo, R. [University of Tasmania, Private Bag 37, GPO Hobart, 7001 (Australia)
2007-06-19
I show how the observed particle spectrum in its various flavors and generations can be accommodated within a scheme involving five complex anticommuting Lorentz scalar coordinates {zeta}, carrying 'property'. A general relativistic extension of the scheme shows that gravity lies in the x - x sector, gauge fields in the x - {zeta} sector and Higgs field in the {zeta} - {zeta} sector.
ERIC Educational Resources Information Center
Newburgh, Ronald
2010-01-01
It's both surprising and rewarding when an old, standard problem reveals a subtlety that expands its pedagogic value. I realized recently that the role of gravity in the range equation for a projectile is not so simple as first appears. This realization may be completely obvious to others but was quite new to me.
Bao, Ruoyu; /Chicago U., EFI /Chicago U.; Carena, Marcela; /Fermilab; Lykken, Joseph; /Chicago U., EFI /Chicago U. /Fermilab; Park, Minjoon; /Chicago U., EFI /Chicago U.; Santiago, Jose; /Fermilab
2005-11-01
Gravity in five-dimensional braneworld backgrounds often exhibits problematic features, including kinetic ghosts, strong coupling, and the vDVZ discontinuity. These problems are an obstacle to producing and analyzing braneworld models with interesting and potentially observable modifications of 4d gravity. We examine these problems in a general AdS{sub 5}/AdS{sub 4} setup with two branes and localized curvature from arbitrary brane kinetic terms. We use the interval approach and an explicit ''straight'' gauge-fixing. We compute the complete quadratic gauge-fixed effective 4d action, as well as the leading cubic order corrections. We compute the exact Green's function for gravity as seen on the brane. In the full parameter space, we exhibit the regions which avoid kinetic ghosts and tachyons. We give a general formula for the strong coupling scale, i.e. the energy scale at which the linearized treatment of gravity breaks down, for relevant regions of the parameter space. We show how the vDVZ discontinuity can be naturally but nontrivially avoided by ultralight graviton modes. We present a direct comparison of warping versus localized curvature in terms of their effects on graviton mode couplings. We exhibit the first example of DGP-like crossover behavior in a general warped setup.
Bahram Mashhoon
2008-01-14
Mathisson's spin-gravity coupling and its Larmor-equivalent interaction, namely, the spin-rotation coupling are discussed. The study of the latter leads to a critical examination of the basic role of locality in relativistic physics. The nonlocal theory of accelerated systems is outlined and some of its implications are described.
Acausality of massive gravity.
Deser, S; Waldron, A
2013-03-15
We show, by analyzing its characteristics, that the ghost-free, 5 degree of freedom, Wess-Zumino massive gravity model admits superluminal shock wave solutions and thus is acausal. Ironically, this pathology arises from the very constraint that removes the (sixth) Boulware-Deser ghost mode. PMID:25166520
Yakov Itin
2007-11-27
The possible extensions of GR for description of fermions on a curved space, for supergravity and for loop quantum gravity require a richer set of 16 independent variables. These variables can be assembled in a coframe field, i.e., a local set of four linearly independent 1-forms. In the ordinary formulation, the coframe gravity does not have any connection to a specific geometry even being constructed from the geometrical meaningful objects. A geometrization of the coframe gravity is an aim of this paper. We construct a complete class of the coframe connections which are linear in the first order derivatives of the coframe field on an $n$ dimensional manifolds with and without a metric. The subclasses of the torsion-free, metric-compatible and flat connections are derived. We also study the behavior of the geometrical structures under local transformations of the coframe. The remarkable fact is an existence of a subclass of connections which are invariant when the infinitesimal transformations satisfy the Maxwell-like system of equations. In the framework of the coframe geometry construction, we propose a geometrical action for the coframe gravity. It is similar to the Einstein-Hilbert action of GR, but the scalar curvature is constructed from the general coframe connection. We show that this geometric Lagrangian is equivalent to the coframe Lagrangian up to a total derivative term. Moreover there is a family of coframe connections which Lagrangian does not include the higher order terms at all. In this case, the equivalence is complete.
NSDL National Science Digital Library
Michael Horton
2009-05-30
This lab is between a Level 2 and Level 3 inquiry activity in that it should be assigned after students understand acceleration but before they learn about the acceleration gravity. Because there are many sources of error when using a pendulum, students c
T. Damour; A. M. Polyakov
1994-01-01
It is pointed out that string-loop effects may generate matter couplings for the dilaton allowing this scalar partner of the tensorial graviton to stay massless while contributing to macroscopic gravity in a way naturally compatible with existing experimental data. Under a certain assumption of universality of the dilaton coupling functions, the cosmological evolution drives the dilaton towards values where it
Ning Wu
2001-01-01
The quantum gravity is formulated based on principle of local gauge invariance. The model discussed in this paper has local gravitational gauge symmetry and gravitational field appears as gauge field. The problems on quantization and renormalization of the theory are also discussed in this paper. In leading order approximation, the gravitational gauge field theory gives out classical Newton's theory of
M. M. Bennett; P. W. Davis
1976-01-01
Accurate targeting of inertially-guided intercontinental ballistic missiles requires simulating with a high degree of fidelity the gravitational force acting on the missile. An accurate representation is particularly important in the first portion of flight where target miss sensitivity to navigation error is largest. The paper describes the point mass Launch Region Gravity Model (LRGM) representation developed for Minuteman targeting and
F. F. Faria
2014-12-15
In this article we construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depend on the metric tensor and a scalar field, which are considered as the only field variables. We find the vacuum field equations of the theory and the solution of its Newtonian limit.
Zero-current and zero-voltage soft-transition commutation cell for PWM inverters
C. M. O. Stein; H. A. Grundling; H. Pinheiro; J. R. Pinheiro; H. L. Hey
2002-01-01
This paper proposes a universal auxiliary commutation circuit for PWM inverters named the zero current and zero voltage transition (ZCZVT) commutation cell. It provides zero current and zero voltage commutation, simultaneously, during main power devices turn-on and turnoff, with limited di\\/dt and dv\\/dt. As a result, the commutations of the main power devices occur truly without losses. Furthermore, reverse recovery
Zero-point energy in spheroidal geometries
A. R. Kitson; A. I. Signal
2006-01-01
We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.
Zero-point energy in spheroidal geometries
A. R. Kitson; A. I. Signal
2005-12-19
We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.
Gravitational Zero Point Energy induces Physical Observables
Remo Garattini
2010-02-12
We consider the contribution of Zero Point Energy on the induced Cosmological Constant and on the induced Electric/Magnetic charge in absence of matter fields. The method is applicable to every spherically symmetric background. Extensions to a generic $f(R) $ theory are also allowed. Only the graviton appears to be fundamental to the determination of Zero Point Energy.
CIX. The zero point energy and ? crystals
C. Domb; L. Salter
1952-01-01
The calculations of Montroll of the moments of the frequency spectrum of a number of crystal lattices enable an accurate estimate to be made of the zero point energy of these lattices. It has been customary to use the value 9\\/8k?, based on the Debye approximation, to estimate the zero point energy, and it is shown that this formula is
Zeros of expansions in orthogonal polynomials
A. Iserles; E. B. Saff
1989-01-01
The theory of bi-orthogonal polynomials is exploited to investigate the location of zeros of truncated expansions in orthogonal polynomials. It turns out that, subject to additional conditions, these zeros can be confined to certain real intervals. Two general techniques are being used: the first depends on a theorem that links strict sign consistency of a generating function to loci of
Zero Tolerance Policies. ERIC Digest Number 146.
ERIC Educational Resources Information Center
McAndrews, Tobin
State legislatures and school boards are adopting a growing number of zero-tolerance polices toward weapons, guns, and violence. Zero-tolerance polices are rules intended to address specific school-safety issues. They have arisen in part as a response to the threat of the withdrawal of federal funds under the 1994 Gun-Free Schools Act, and
Student Dress Codes Using Zero Tolerance?
ERIC Educational Resources Information Center
Essex, Nathan L.
2004-01-01
In this article, the author focuses on the issue involving zero tolerance in the Texas district whether the dress code policy is reasonable. In a small Texas school district, over 700 students were suspended in a single month for violating a zero-tolerance dress code policy. This suspension, which attracted national attention and threats of
Join the ZERO TO THREE Policy Network
ERIC Educational Resources Information Center
Lally, J. Ronald; Lurie-Hurvitz, Erica; Cohen, Julie
2006-01-01
The authors describe the new ZERO TO THREE Policy Network, launched in 2005 to help the early childhood community get involved with public policy. The purpose of the ZERO TO THREE Policy Network is to engage infant-toddler professionals, researchers, and advocates in the public policy process and provide them with the tools and information they
Zero-point momentum in Complex media
B. A. van Tiggelen
2007-06-22
In this work we apply field regularization techniques to formulate a number of new phenomena related to momentum induced by electromagnetic zero-point fluctuations. We discuss the zero-point momentum associated with magneto-electric media, with moving media, and with magneto-chiral media.
Zero-Base Budgeting:; An Institutional Experience.
ERIC Educational Resources Information Center
Alexander, Donald L.; Anderson, Roger C.
Zero-base budgeting as it is used at Allegany College is described. Zero-based budgeting is defined as a budgeting and planning approach that requires the examination of every item in a budget request as if the request were being proposed for the first time. Budgets (decision packages) are first made up for decision units (i.e., a course for the
NET-ZERO ENERGY HIGH PERFORMANCE
Farritor, Shane
was that the largest potential for enhancing energy supplies in this country is making buildings more efficient. "-- Harvey Perlman, UNL Chancellor #12;Net-Zero Energy, High-Performance Green Buildings | 1 INTRODUCTION EXECUTIVE SUMMARY KEYNOTE SPEAKERS The Path to Net-Zero Energy Buildings Greg Stark, Advanced Commercial
Zero-Knowledge Proofs of Identity
Uriel Feige; Amos Fiat; Adi Shamir
1988-01-01
In this paper we extend the notion of interactive proofs of assertions to interactive proofs of knowledge. This leads to the definition of unrestricted input zero-knowledge proofs of knowledge in which the prover demonstrates possession of knowledge without revealing any computational information whatsoever (not even the one bit revealed in zero-knowledge proofs of assertions). We show the relevance of these
Analog systems for gravity duals
NASA Astrophysics Data System (ADS)
Hossenfelder, Sabine
2015-06-01
We show that analog gravity systems exist for charged, planar black holes in asymptotic anti-de Sitter space. These black holes have been employed to describe, via the gauge-gravity duality, strongly coupled condensed matter systems on the boundary of anti-de Sitter (AdS) space. The analog gravity system is a different condensed matter system that, in a suitable limit, describes the same bulk physics as the theory on the AdS boundary. This combination of the gauge-gravity duality and analog gravity therefore suggests a duality between different condensed matter systems.
Analog Systems for Gravity Duals
S. Hossenfelder
2015-06-09
We show that analog gravity systems exist for charged, planar black holes in asymptotic Anti-de Sitter space. These black holes have been employed to describe, via the gauge-gravity duality, strongly coupled condensed matter systems on the boundary of AdS-space. The analog gravity system is a different condensed matter system that, in a suitable limit, describes the same bulk physics as the theory on the AdS boundary. This combination of the gauge-gravity duality and analog gravity therefore suggests a duality between different condensed matter systems.
Industrial processes influenced by gravity
NASA Technical Reports Server (NTRS)
Ostrach, Simon
1988-01-01
In considering new directions for low gravity research with particular regard to broadening the number and types of industrial involvements, it is noted that transport phenomena play a vital role in diverse processes in the chemical, pharmaceutical, food, and biotech industries. Relatively little attention has been given to the role of gravity in such processes. Accordingly, numerous industrial processes and phenomena are identified which involve gravity and/or surface tension forces. Phase separations and mixing are examples that will be significantly different in low gravity conditions. A basis is presented for expanding the scope of the low gravity research program and the potential benefits of such research is indicated.
Fulvio Sbisa'
2014-07-09
The recent observational data in cosmology seem to indicate that the universe is currently expanding in an accelerated way. An intriguing interpretation of these data is that they may just be signalling that Einstein's General Relativity is not the correct description of gravity when we consider distances of the order of the present horizon of the universe. In this thesis we consider two models which modify General Relativity at very large distances, the Cascading DGP and the dRGT massive gravity, and investigate their phenomenological viability. We start with a general introduction to standard cosmology and we introduce the late time acceleration problem and the cosmological constant problem. We then provide a pedagogical introduction to the DGP model, of which the Cascading DGP is an extension, and to the dRGT massive gravity. Concerning the Cascading DGP, we show that the thin limit of the 4D brane inside the (already thin) 5D brane is well defined, at least for the class of configurations that we consider, and confirm that gravity is regularized in these set-ups. We give a geometrical interpretation of the presence of the critical tension, and comment on the difference between the results in the literature and our results, which we support with a numerical calculation. Regarding the dRGT massive gravity, we focus on the branch of solutions in which the Vainshtein mechanism can occur. We determine analytically the number and properties of local solutions which exist asymptotically on large scales (but still below the gravitational Compton wavelength), and of local (inner) solutions which exist on small scales. We characterize exactly the properties of global solutions in every point of the phase space, and characterize precisely in which regions the Vainshtein mechanism takes place. We also provide numerical solutions which confirm our analysis.
NASA Astrophysics Data System (ADS)
Schutz, Bernard
2003-12-01
Preface; 1. Gravity on Earth: the inescapable force; 2. And then came Newton: gravity takes center stage; 3. Satellites: what goes up doesn't always come down; 4. The Solar System: a triumph for Newtonian gravity; 5. Tides and tidal forces: the real signature of gravity; 6. Interplanetary travel: the cosmic roller-coaster; 7. Atmospheres: keeping planets covered; 8. Gravity in the Sun: keeping the heat on; 9. Reaching for the stars: the emptiness of outer space; 10. The colors of stars: why they are black (bodies); 11. Stars at work: factories for the Universe; 12. Birth to death: the life cycle of the stars; 13. Binary stars: tidal forces on a huge scale; 14. Galaxies: atoms in the Universe; 15. Physics near the speed of light: Einstein stands on Galileo's shoulders; 16. Relating to Einstein: logic and experiment in relativity; 17. Spacetime geometry: finding out what is not relative; 18. Einstein's gravity: the curvature of spacetime in the Solar System; 19. Einstein's recipe: fashioning the geometry of gravity; 20. Neutron stars: laboratories of strong gravity; 21. Black holes: gravity's one-way street; 22. Gravitational waves: gravity speaks; 23. Gravitational lenses: bringing the Universe into focus; 24. Cosmology: the study of everything; 25. Big Bang: the seed from which we grew; 26. Einstein's Universe: the geometry of cosmology; 27. Ask the Universe: cosmic questions at the frontiers of gravity; Appendix A. Useful constants: values used in this book; Appendix B. Background: what you need to know before you start.
Quantum Gravity from Noncommutative Spacetime
Jungjai Lee; Hyun Seok Yang
2014-11-25
We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative $\\star$-algebra) of quantum gravity.
I. Matsuyama; F. Nimmo
2009-01-01
We consider the effect of spin-orbit resonance, nonzero eccentricity, despinning, and reorientation on Mercury's gravity and tectonic pattern. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J2\\/C22 = 10\\/3 and (b ? c)\\/(a ? c) = 1\\/4, arise because of nonsynchronous rotation and nonzero eccentricity even in the absence of reorientation or
I. Matsuyama; F. Nimmo
2009-01-01
We consider the effect of spin-orbit resonance, nonzero eccentricity, despinning, and reorientation on Mercury's gravity and tectonic pattern. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J 2\\/C 22 = 10\\/3 and (b - c)\\/(a - c) = 1\\/4, arise because of nonsynchronous rotation and nonzero eccentricity even in the absence of
Rotating gravity currents. Part 1. Energy loss theory
NASA Astrophysics Data System (ADS)
Martin, J. R.; Lane-Serff, G. F.
2005-01-01
A comprehensive energy loss theory for gravity currents in rotating rectangular channels is presented. The model is an extension of the non-rotating energy loss theory of Benjamin (J. Fluid Mech. vol. 31, 1968, p. 209) and the steady-state dissipationless theory of rotating gravity currents of Hacker (PhD thesis, 1996). The theory assumes the fluid is inviscid, there is no shear within the current, and the Boussinesq approximation is made. Dissipation is introduced using a simple method. A head loss term is introduced into the Bernoulli equation and it is assumed that the energy loss is uniform across the stream. Conservation of momentum, volume flux and potential vorticity between upstream and downstream locations is then considered. By allowing for energy dissipation, results are obtained for channels of arbitrary depth and width (relative to the current). The results match those from earlier workers in the two limits of (i) zero rotation (but including dissipation) and (ii) zero dissipation (but including rotation). Three types of flow are identified as the effect of rotation increases, characterized in terms of the location of the outcropping interface between the gravity current and the ambient fluid on the channel boundaries. The parameters for transitions between these cases are quantified, as is the detailed behaviour of the flow in all cases. In particular, the speed of the current can be predicted for any given channel depth and width. As the channel depth increases, the predicted Froude number tends to surd 2, as for non-rotating flows.
Scattering amplitudes in super-renormalizable gravity
Pietro Donŕ; Stefano Giaccari; Leonardo Modesto; Leslaw Rachwal; Yiwei Zhu
2015-06-15
We explicitly compute the tree-level on-shell four-graviton amplitudes in four, five and six dimensions for local and weakly nonlocal gravitational theories that are quadratic in both, the Ricci and scalar curvature with form factors of the d'Alembertian operator inserted between. More specifically we are interested in renormalizable, super-renormalizable or finite theories. The scattering amplitudes for these theories turn out to be the same as the ones of Einstein gravity regardless of the explicit form of the form factors. As a special case the four-graviton scattering amplitudes in Weyl conformal gravity are identically zero. Using a field redefinition, we prove that the outcome is correct for any number of external gravitons (on-shell $n-$point functions) and in any dimension for a large class of theories. However, when an operator quadratic in the Riemann tensor is added in any dimension (with the exception of the Gauss-Bonnet term in four dimensions) the result is completely altered, and the scattering amplitudes depend on all the form factors introduced in the action.
Scattering amplitudes in super-renormalizable gravity
Donŕ, Pietro; Modesto, Leonardo; Rachwal, Leslaw; Zhu, Yiwei
2015-01-01
We explicitly compute the tree-level on-shell four-graviton amplitudes in four, five and six dimensions for local and weakly nonlocal gravitational theories that are quadratic in both, the Ricci and scalar curvature with form factors of the d'Alembertian operator inserted between. More specifically we are interested in renormalizable, super-renormalizable or finite theories. The scattering amplitudes for these theories turn out to be the same as the ones of Einstein gravity regardless of the explicit form of the form factors. As a special case the four-graviton scattering amplitudes in Weyl conformal gravity are identically zero. Using a field redefinition, we prove that the outcome is correct for any number of external gravitons (on-shell $n-$point functions) and in any dimension for a large class of theories. However, when an operator quadratic in the Riemann tensor is added in any dimension (with the exception of the Gauss-Bonnet term in four dimensions) the result is completely altered, and the scattering...
Planckian Axions and the Weak Gravity Conjecture
Bachlechner, Thomas C; McAllister, Liam
2015-01-01
Several recent works have claimed that the Weak Gravity Conjecture (WGC) excludes super-Planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. We argue that in theories with $N\\gg1$ axions, super-Planckian axion diameters $\\cal{D}$ are readily allowed by the WGC. We clarify the nontrivial relationship between the kinetic matrix $K$ --- unambiguously defined by its form in a Minkowski-reduced basis --- and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues $f_1^2 \\le ... \\le f_N^2$ of $K$: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. In particular, even if one were to impose the condition $f_NM_{pl}$ does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. Finally, we argue that in effective axion-gravity theories, the zero-form version of the WGC can be satisf...
Planckian Axions and the Weak Gravity Conjecture
Thomas C. Bachlechner; Cody Long; Liam McAllister
2015-03-26
Several recent works have claimed that the Weak Gravity Conjecture (WGC) excludes super-Planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. We argue that in theories with $N\\gg1$ axions, super-Planckian axion diameters $\\cal{D}$ are readily allowed by the WGC. We clarify the nontrivial relationship between the kinetic matrix $K$ --- unambiguously defined by its form in a Minkowski-reduced basis --- and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues $f_1^2 \\le ... \\le f_N^2$ of $K$: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. In particular, even if one were to impose the condition $f_NM_{pl}$ does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. Finally, we argue that in effective axion-gravity theories, the zero-form version of the WGC can be satisfied by gravitational instantons that make negligible contributions to the potential.
Reggeon exchange from gauge/gravity duality
NASA Astrophysics Data System (ADS)
Giordano, Matteo; Peschanski, Robi
2011-10-01
We perform the analysis of quark-antiquark Reggeon exchange in meson-meson scattering, in the framework of the gauge/gravity correspondence in a confining background. On the gauge theory side, Reggeon exchange is described as quark-antiquark exchange in the t channel between fast projectiles. The corresponding amplitude is represented in terms of Wilson loops running along the trajectories of the constituent quarks and antiquarks. The paths of the exchanged fermions are integrated over, while the "spectator" fermions are dealt with in an eikonal approximation. On the gravity side, we follow a previously proposed approach, and we evaluate the Wilson-loop expectation value by making use of gauge/gravity duality for a generic confining gauge theory. The amplitude is obtained in a saddle-point approximation through the determination near the confining horizon of a Euclidean "minimal surface with floating boundaries", i.e., by fixing the trajectories of the exchanged quark and antiquark by means of a minimisation procedure, which involves both area and length terms. After discussing, as a warm-up exercise, a simpler problem on a plane involving a soap film with floating boundaries, we solve the variational problem relevant to Reggeon exchange, in which the basic geometry is that of a helicoid. A compact expression for the Reggeon-exchange amplitude, including the effects of a small fermion mass, is then obtained through analytic continuation from Euclidean to Minkowski space-time. We find in particular a linear Regge trajectory, corresponding to a Regge-pole singularity supplemented by a logarithmic cut induced by the non-zero quark mass. The analytic continuation leads also to companion contributions, corresponding to the convolution of the same Reggeon-exchange amplitude with multiple elastic rescattering interactions between the colliding mesons.
Locomotion in simulated microgravity: gravity replacement loads
NASA Technical Reports Server (NTRS)
McCrory, Jean L.; Baron, Heidi A.; Balkin, Sandy; Cavanagh, Peter R.
2002-01-01
BACKGROUND: When an astronaut walks or runs on a treadmill in microgravity, a subject load device (SLD) is used to return him or her back to the treadmill belt. The gravity replacement load (GRL) in the SLD is transferred, via a harness, to the pelvis and/or the shoulders. This research compared comfort and ground reaction forces during treadmill running in a microgravity locomotion simulator at GRLs of 60%, 80%, and 100% of body weight (BW). Two harness designs (shoulder springs only (SSO) and waist and shoulder springs (WSS)) were used. HYPOTHESES: 1) The 100% BW gravity replacement load conditions would be comfortably tolerated and would result in larger ground reaction forces and loading rates than the lower load conditions, and 2) the WSS harness would be more comfortable than the SSO harness. METHODS: Using the Penn State Zero Gravity Locomotion Simulator (ZLS), 8 subjects ran at 2.0 m x s(-1) (4.5 mph) for 3 min at each GRL setting in each harness. Subjective ratings of harness comfort, ground reaction forces, and GRL data were collected during the final minute of exercise. RESULTS: The 100% BW loading conditions were comfortably tolerated (2.3 on a scale of 0-10), although discomfort increased as the GRL increased. There were no overall differences in perceived comfort between the two harnesses. The loading rates (27.1, 33.8, 39.1 BW x s(-1)) and the magnitudes of the first (1.0, 1.4, 1.6 BW) and second (1.3, 1.7, 1.9 BW) peaks of the ground reaction force increased with increasing levels (60, 80, 100% BW respectively) of GRL. CONCLUSIONS: Subjects were able to tolerate a GRL of 100% BW well. The magnitude of the ground reaction force peaks and the loading rate is directly related to the magnitude of the GRL.
Validity of semiclassical gravity in the stochastic gravity approach
E. Verdaguer
2005-07-18
In semiclassical gravity the back-reaction of the classical gravitational field interacting with quantum matter fields is described by the semiclassical Einstein equations. A criterion for the validity of semiclassical gravity based on the stability of the solutions of the semiclassical Einstein equations with respect to quantum metric perturbations is discussed. The two-point quantum correlation functions for the metric perturbations can be described by the Einstein-Langevin equation obtained in the framework of stochastic gravity. These correlation functions agree, to leading order in the large $N$ limit, with the quantum correlation functions of the theory of gravity interacting with $N$ matter fields. The Einstein-Langevin equations exhibit runaway solutions and methods to deal with these solutions are discussed. The validity criterion is used to show that flat spacetime as a solution of semiclassical gravity is stable and, consequently, a description based on semiclassical gravity is a valid approximation in that case.
Zero Modes for the Boundary Giant Magnons
Dongsu Bak
2009-01-19
We study the fermion zero-mode dynamics for open strings ending on the giant graviton branes. For the open string ending on the Z=0 brane, the quantization of the fermion zero-modes of boundary giant magnons reproduces the 256 states of the boundary degrees with the precise realization of the SU(2|2) X SU(2|2) symmetry algebra. Also for the open string ending on the Y=0 brane, we reproduce the unique vacuum state from the fermion zero-modes.
NASA Astrophysics Data System (ADS)
Blind, N.; Eisenhauer, F.; Haug, M.; Gillessen, S.; Lippa, Magdalena; Burtscher, L.; Hans, O.; Haussmann, F.; Huber, S.; Janssen, A.; Kellner, S.; Kok, Y.; Ott, T.; Pfuhl, O.; Sturm, E.; Weber, J.; Wieprecht, E.; Amorim, A.; Brandner, W.; Perrin, G.; Perraut, K.; Straubmeier, C.
2014-07-01
We present in this paper the design and characterisation of a new sub-system of the VLTI 2nd generation instrument GRAVITY: the Calibration Unit. The Calibration Unit provides all functions to test and calibrate the beam combiner instrument: it creates two artificial stars on four beams, and dispose of four delay lines with an internal metrology. It also includes artificial stars for the tip-tilt and pupil guiding systems, as well as four metrology pick-up diodes, for tests and calibration of the corresponding sub-systems. The calibration unit also hosts the reference targets to align GRAVITY to the VLTI, and the safety shutters to avoid the metrology light to propagate in the VLTI-lab. We present the results of the characterisation and validtion of these differrent sub-units.
Gravity wave initiated convection
NASA Astrophysics Data System (ADS)
Hung, R. J.
1990-09-01
The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.
Asymptotically Safe Lorentzian Gravity
Elisa Manrique; Stefan Rechenberger; Frank Saueressig
2011-02-24
The gravitational asymptotic safety program strives for a consistent and predictive quantum theory of gravity based on a non-trivial ultraviolet fixed point of the renormalization group (RG) flow. We investigate this scenario by employing a novel functional renormalization group equation which takes the causal structure of space-time into account and connects the RG flows for Euclidean and Lorentzian signature by a Wick-rotation. Within the Einstein-Hilbert approximation, the $\\beta$-functions of both signatures exhibit ultraviolet fixed points in agreement with asymptotic safety. Surprisingly, the two fixed points have strikingly similar characteristics, suggesting that Euclidean and Lorentzian quantum gravity belong to the same universality class at high energies.
Reality in Noncommutative Gravity
B. M. Zupnik
2006-10-24
We study the problem of reality in the geometric formalism of the 4D noncommutative gravity using the known deformation of the diffeomorphism group induced by the twist operator with the constant deformation parameters $\\vt^{mn}$. It is shown that real covariant derivatives can be constructed via $\\star$-anticommutators of the real connection with the corresponding fields. The minimal noncommutative generalization of the real Riemann tensor contains only $\\vt^{mn}$-corrections of the even degrees in comparison with the undeformed tensor. The gauge field $h_{mn}$ describes a gravitational field on the flat background. All geometric objects are constructed as the perturbation series using $\\star$-polynomial decomposition in terms of $h_{mn}$. We consider the nonminimal tensor and scalar functions of $h_{mn}$ of the odd degrees in $\\vt^{mn}$ and remark that these pure noncommutative objects can be used in the noncommutative gravity.
Collected Calculations in Quantum Gravity and QED
NASA Astrophysics Data System (ADS)
Sawhill, Bruce Kean
In the first part of this thesis, I present a calculation of the helicity amplitudes of electron-positron double bremsstrahlung in the massless limit. Using a representation for free photon polarizations developed by a group of European physicists, helicity amplitudes for double bremsstrahlung in the massless limit are calculated for all possible combinations of helicities in the two incoming and four outgoing particle states. The calculation is made possible by the vast simplification which occurs at the amplitude level because of the gauge cancellations caused by expressing the photon polarizations in terms of the fermion momenta to which they are attached. The results of the calculation are discussed in terms of possible use as a polarization monitor for future generations of colliding beam machines in which the beams could be polarized. It is found that, although the total cross-section is easily measured experimentally, the polarization asymmetry is very difficult to measure unless the flux is very high. The possibility of using double bremsstrahlung as a means of analyzing the zed-zero is discussed. The applications for this purpose are very promising, as the shape and amplitude of the cross-section are very dependent on the chiral structure of the mediating particle. In the second part of this work, I present a calculation of the cosmological constant to two loops in matterless quantum gravity. A quantization method originally developed by 't Hooft and Veltman and later modified by M. Mueller is used. This is the standard path integral formulation of gravity modified such that it takes into account the dependence of the action functional on the fluctuating metric, an effect which is normally discarded because dimensional regularization nullifies its contributions. The purpose of the calculation was to explore more fully an intriguing result found by Mark Mueller while performing the same calculation to one-loop order; namely, the quantum corrections to the cosmological constant were identically zero independent of the regularization scheme used regulate the loop integrals, as the coefficients of these integrals identically cancelled for any number of space-time dimensions. In performing the two-loop calculation it was found that the one-loop result no longer holds, and that a regularization scheme must be specified. The possibility of using higher-derivative couplings in gravity is discussed as a means of cutting off the loop-momentum integrals.
Covariant Loop Quantum Gravity
NASA Astrophysics Data System (ADS)
Rovelli, Carlo; Vidotto, Francesca
2014-11-01
Preface; Part I. Foundations: 1. Spacetime as a quantum object; 2. Physics without time; 3. Gravity; 4. Classical discretization; Part II. The 3D Theory: 5. 3D Euclidean theory; 6. Bubbles and cosmological constant; Part III. The Real World: 7. The real world: 4D Lorentzian theory; 8. Classical limit; 9. Matter; Part IV. Physical Applications: 10. Black holes; 11. Cosmology; 12. Scattering; 13. Final remarks; References; Index.
Hughes, R.J.; Goldman, T.; Nieto, M.M.
1988-01-01
Preliminary results of the test of the Newtonian Law of Gravitation conducted by Ander et al., in a borehole in the Greenland ice-cap were reported at this meeting. In this paper we consider the interpretations of these results in terms of a non-Newtonian component of gravity, and compare them with the results of other geophysical inverse-square law tests. 8 refs.
Gravity, Time, and Lagrangians
ERIC Educational Resources Information Center
Huggins, Elisha
2010-01-01
Feynman mentioned to us that he understood a topic in physics if he could explain it to a college freshman, a high school student, or a dinner guest. Here we will discuss two topics that took us a while to get to that level. One is the relationship between gravity and time. The other is the minus sign that appears in the Lagrangian. (Why would one
NASA Technical Reports Server (NTRS)
Bell, C. C.
1971-01-01
The results of the noise and drift test, and the comparison of the experimental simulation tests with the theoretical predictions, confirm that the rotating gravity gradiometer is capable of extracting information about mascon distributions from lunar orbit, and that the sensitivity of the sensor is adequate for lunar orbital selenodesy. The experimental work also verified analytical and computer models for the directional and time response of the sensor.
Stephen D. Eckermann; Peter Preusse; Bernd Schaeler; Jens Oberheide; Dirk Offerman; Julio T. Bacmeister; Dave Broutman
We describe a preliminary analysis of small-scale temperature perturbations in the stratosphere produced by long wavelength gravity waves, as measured globally during the CRISTA-SPAS missions. We focus on enhanced activity observed at the equator and near the southern tip of South America. Global ray-tracing simulations for the mission days indicate that the equatorial activity is broadly consistent with the transmission
Iver Brevik
2012-11-23
A bulk viscosity is introduced in the formalism of modified gravity. It is shown that, on the basis of a natural scaling law for the viscosity, a simple solution can be found for quantities such as the Hubble parameter and the energy density. These solutions may incorporate a viscosity-induced Big Rip singularity. By introducing a phase transition in the cosmic fluid, the future singularity can nevertheless in principle be avoided.
R. Bluhm
2013-07-22
Gravitational theories with Lorentz violation must account for a number of possible features in order to be consistent theoretically and phenomenologically. A brief summary of these features is given here. They include evasion of a no-go theorem, connections between spontaneous Lorentz breaking and diffeomorphism breaking, the appearance of massless Nambu-Goldstone modes and massive Higgs modes, and the possibility of a Higgs mechanism in gravity.
NSDL National Science Digital Library
Students take a series of gravity measurements to estimate the height of the walkway near the top of the atrium in Howe-Russell. Students turn in a copy of the data sheet plus 1) an explanation of how they converted dial measurements to mgals; 2) plot of instrument drift/Earth tides correction; 3) estimate of elevation of the walkway using a Free-Air Correction; and 4) a brief (paragraph or two) discussion of potential errors in the survey.
Gravity field information from Gravity Probe-B
NASA Technical Reports Server (NTRS)
Smith, D. E.; Lerch, F. J.; Colombo, O. L.; Everitt, C. W. F.
1989-01-01
The Gravity Probe-B Mission will carry the Stanford Gyroscope relativity experiment into orbit in the mid 1990's, as well as a Global Positioning System (GPS) receiver whose tracking data will be used to study the earth gravity field. Estimates of the likely quality of a gravity field model to be derived from the GPS data are presented, and the significance of this experiment to geodesy and geophysics are discussed.
Massive Gravity from Higher Derivative Gravity with Boundary Conditions
Minjoon Park; Lorenzo Sorbo
2012-10-29
With an appropriate choice of parameters, a higher derivative theory of gravity can describe a normal massive sector and a ghost massless sector. We show that, when defined on an asymptotically de Sitter spacetime with Dirichlet boundary conditions, such a higher derivative gravity can provide a framework for a unitary theory of massive gravity in four spacetime dimensions. The resulting theory is free not only of higher derivative ghosts but also of the Boulware-Deser mode.
NASA Technical Reports Server (NTRS)
Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.; Steinberg, S. L. (Principal Investigator)
2005-01-01
Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.
Granular Superconductors and Gravity
NASA Technical Reports Server (NTRS)
Noever, David; Koczor, Ron
1999-01-01
As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lake, Matthew J.
2015-02-01
We consider Kasner-type static, cylindrically symmetric interior string solutions in the theory of modified gravity. The physical properties of the string are described by an anisotropic energy-momentum tensor satisfying the condition ; that is, the energy density of the string along the -axis is equal to minus the string tension. As a first step in our study we obtain the gravitational field equations in the theory for a general static, cylindrically symmetric metric, and then for a Kasner-type metric, in which the metric tensor components have a power law dependence on the radial coordinate . String solutions in two particular modified gravity models are investigated in detail. The first is the so-called "exponential" modified gravity, in which the gravitational action is proportional to the exponential of the sum of the Ricci scalar and matter Lagrangian, and the second is the "self-consistent model", obtained by explicitly determining the gravitational action from the field equations under the assumption of a power law dependent matter Lagrangian. In each case, the thermodynamic parameters of the string, as well as the precise form of the matter Lagrangian, are explicitly obtained.
Luis Alvarez-Gaume; Alex Kehagias; Costas Kounnas; Dieter Lust; Antonio Riotto
2015-05-28
We discuss quadratic gravity where terms quadratic in the curvature tensor are included in the action. After reviewing the corresponding field equations, we analyze in detail the physical propagating modes in some specific backgrounds. First we confirm that the pure $R^2$ theory is indeed ghost free. Then we point out that for flat backgrounds the pure $R^2$ theory propagates only a scalar massless mode and no spin-two tensor mode. However, the latter emerges either by expanding the theory around curved backgrounds like de Sitter or anti-de Sitter, or by changing the long-distance dynamics by introducing the standard Einstein term. In both cases, the theory is modified in the infrared and a propagating graviton is recovered. Hence we recognize a subtle interplay between the UV and IR properties of higher order gravity. We also calculate the corresponding Newton's law for general quadratic curvature theories. Finally, we discuss how quadratic actions may be obtained from a fundamental theory like string- or M-theory. We demonstrate that string theory on non-compact $CY_3$ manifolds, like a line bundle over $\\mathbb{CP}^2$, may indeed lead to gravity dynamics determined by a higher curvature action.
Quantum gravity and renormalization
NASA Astrophysics Data System (ADS)
Anselmi, Damiano
2015-01-01
The properties of quantum gravity are reviewed from the point of view of renormalization. Various attempts to overcome the problem of non-renormalizability are presented, and the reasons why most of them fail for quantum gravity are discussed. Interesting possibilities come from relaxing the locality assumption, which also can inspire the investigation of a largely unexplored sector of quantum field theory. Another possibility is to work with infinitely many independent couplings, and search for physical quantities that only depend on a finite subset of them. In this spirit, it is useful to organize the classical action of quantum gravity, determined by renormalization, in a convenient way. Taking advantage of perturbative local field redefinitions, we write the action as the sum of the Hilbert term, the cosmological term, a peculiar scalar that is important only in higher dimensions, plus invariants constructed with at least three Weyl tensors. We show that the FRLW configurations, and many other locally conformally flat metrics, are exact solutions of the field equations in arbitrary dimensions d>3. If the metric is expanded around such configurations the quadratic part of the action is free of higher-time derivatives. Other well-known metrics, such as those of black holes, are instead affected in nontrivial ways by the classical corrections of quantum origin.
NASA Astrophysics Data System (ADS)
O'Sullivan, Ian
2014-03-01
The speed of light is measured as a constant number of metres per second. However, a meter is a measure of how far light travels in a second. That is, light always travels as far as it does in a second every second. This is a circular definition. When measured against other things, light speed must change. Gravity is usually described as a consequence of a curve in spacetime. The word ``space'' has two distinct meanings. In geometry, space is a continuous area. In relativity, ``space'' refers exclusively to geometric spaces measured with light. ``Time'' in a relativistic sense also refers exclusively to the passage of time as measured against light. So a curve in spacetime (a relativistic concept) is a gradual deviation in the thing we use to measure geometric spaces and the passage of time, i.e. the speed of light. I show how Newtonian gravity can explain observable phenomena if the speed of light is inversely proportional to the strength of the gravitational field. For example, we would also expect light to refract as it changes speed passing near massive bodies. Boundary conditions are also discussed, for example, very high gravity will slow light to a stop, making it impossible to measure anything against light, giving a gravitational singularity.
The frequency characteristic research based on the zero and pole
Pang Jiao; Wang Lan-xun; Tian Xiao-yan; Li Cai-xia
2010-01-01
Quantificational calculational method was adopted. The effect of single zero and pole and conjugate zero and pole to the frequency response of the system was analyzed, which explained frequency of breadth frequency valve value and peak value with the frequency of the zero and pole locality strictly accorded, when it was single zero and pole and conjugate zero and pole
Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS
NASA Technical Reports Server (NTRS)
Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Geiger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)
2003-01-01
A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water. The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles
On Zero Stiffness Mark Schenk and Simon D Guest
Guest, Simon
preprint On Zero Stiffness Mark Schenk and Simon D Guest Abstract Zero stiffness structures have and iv) zero stiffness. Each perspective on zero stiffness provides different methods of analysis and design. This paper reviews the concept of zero stiffness and categorises examples from the literature
Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs
NASA Technical Reports Server (NTRS)
Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)
2006-01-01
A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.
NASA Astrophysics Data System (ADS)
Miwa, Akitsugu
2015-05-01
We reconsider a gravity dual of a 1 /4 BPS Wilson loop. In the case of an expectation value of the Wilson loop, it is known that broken zero modes of a string world sheet in the gravity side play important roles in the limit ? ??, keeping the combination ? cos2?0 finite. Here, ? is the 't Hooft coupling constant and ?0 is a parameter of the Wilson loop. In this paper, we reconsider a gravity dual of a correlation function between the Wilson loop and a 1 /2 BPS local operator with R charge J . We take account of contributions coming from the same configurations of the above-mentioned broken zero modes. We find an agreement with the gauge theory side in the limit J ??{? cos2?0 } .
100 years of gravity and accelerated frames
NASA Astrophysics Data System (ADS)
Hsu, J. P.; Fine, Dana
The dawn of gravitation -- Einstein's deepest insight and its early impacts -- The scalar-tensor theory of gravity -- Yang-Mills' deepest insight and its relation to gravity -- Accelerated frames: Generalizing the Lorentz transformations -- Quantum gravity and 'Ghosts' -- Gauge theories of gravity -- Alternate approaches to gravity: Roads less traveled by -- Experimental tests of gravitational theories -- Other perspectives.
On zero energy states in graphene
C. -L. Ho; P. Roy
2014-10-02
We obtain zero energy states in graphene for a number of potentials and discuss the relation of the decoupled Schr\\"odinger-like equations for the the spinor components with non relativistic $\\cal{PT}$ symmetric quantum mechanics.
Zero Location for Nonstandard Orthogonal Polynomials
Antonio J. Durán Guardeńo; Edward B. Saff
2001-01-01
A method to locate the zeros of orthogonal polynomials with respect to nonstandard inner products is discussed and applied to Sobolev orthogonal polynomials and polynomials satisfying higher-order recurrence relations.
Zero tolerance: unfair, with little recourse.
Browne, J A; Losen, D J; Wald, J
2001-01-01
This chapter examines racial disparities in the application of zero tolerance, describes legal avenues available to parents and children's advocates, and summarizes recent court decisions issued on school discipline cases. PMID:12170831
The Zero-Point Field and Inertia
Bernhard Haisch; Alfonso Rueda
1999-08-19
A brief overview is presented of the basis of the electromagnetic zero-point field in quantum physics and its representation in stochastic electrodynamics. Two approaches have led to the proposal that the inertia of matter may be explained as an electromagnetic reaction force. The first is based on the modeling of quarks and electrons as Planck oscillators and the method of Einstein and Hopf to treat the interaction of the zero-point field with such oscillators. The second approach is based on analysis of the Poynting vector of the zero-point field in accelerated reference frames. It is possible to derive both Newton's equation of motion, F=ma, and its relativistic co-variant form from Maxwell's equations as applied to the zero-point field of the quantum vacuum. This appears to account, at least in part, for the inertia of matter.
ZERO SITE MANUAL ZACKENBERG ECOLOGICAL RESEARCH OPERATIONS
ZERO SITE MANUAL ZACKENBERG ECOLOGICAL RESEARCH OPERATIONS Zackenberg secretariat Department The Zackenberg Ecological Research Operations (at the Department of Bioscience, Aarhus University) appreciates ecosystem research in the high Arctic. According to the framework programme of Zackenberg Ecological
Zero-Based Budgeting in Nursing Education.
ERIC Educational Resources Information Center
Farrell, Marie; Eckert, Joseph
1979-01-01
Zero-based budgeting (ZBB) refers to a system whereby the entire nursing program is reevaluated yearly and justification for all programs and expenditures must be made. ZBB is compared to the governmental sunset law. (JOW)
Fingerprints Theorems for Zero-Crossings
Yuille, A.L.
1983-10-01
We prove that the scale map of the zero-crossings of almost all signals filtered by the second derivative of a gaussian of variable size determines the signal uniquely, up to a constant scaling and a harmonic function. ...
NASA Technical Reports Server (NTRS)
Ostrach, S.
1982-01-01
The behavior of fluids in micro-gravity conditions is examined, with particular regard to applications in the growth of single crystals. The effects of gravity on fluid behavior are reviewed, and the advent of Shuttle flights are noted to offer extended time for experimentation and processing in a null-gravity environment, with accelerations resulting solely from maneuvering rockets. Buoyancy driven flows are considered for the cases stable-, unstable-, and mixed-mode convection. Further discussion is presented on g-jitter, surface-tension gradient, thermoacoustic, and phase-change convection. All the flows are present in both gravity and null gravity conditions, although the effects of buoyancy and g-jitter convection usually overshadow the other effects while in a gravity field. Further work is recommended on critical-state and sedimentation processes in microgravity conditions.
Utilization of Low Gravity Environment for Measuring Liquid Viscosity
NASA Technical Reports Server (NTRS)
Antar, Basil N.; Ethridge, Edwin
1998-01-01
The method of drop coalescence is used for determining the viscosity of highly viscous undercooled liquids. Low gravity environment is necessary in order to allow for examining large volumes affording much higher accuracy for the viscosity calculations than possible for smaller volumes available under 1 - g conditions. The drop coalescence method is preferred over the drop oscillation technique since the latter method can only be applied for liquids with vanishingly small viscosities. The technique developed relies on both the highly accurate solution of the Navier-Stokes equations as well as on data from experiments conducted in near zero gravity environment. Results are presented for method validation experiments recently performed on board the NASA/KC-135 aircraft. While the numerical solution was produced using the Boundary Element Method. In these tests the viscosity of a highly viscous liquid, glycerine at room temperature, was determined using the liquid coalescence method. The results from these experiments will be discussed.
Zero asymptotic behaviour for orthogonal matrix polynomials
A. J. Duran; P. Lopez-Rodriguez; E. B. Saff
1999-01-01
Weak-star asymptotic results are obtained for the zeros of orthogonal matrix polynomials (i.e., the zeros of their determinants)\\u000a on ? from two different assumptions: first from the convergence of matrix coefficients occurring in the three-term recurrence\\u000a for these polynomials; and, second, from conditions on the generating matrix measure. The matrix analogues of the Chebyshev\\u000a polynomials of the first kind are
Vanishing dynamical quark mass at zero virtuality?
A. E. Dorokhov; W. Broniowski
2001-10-04
We show that the dynamical quark mass in effective nonlocal models can vanish at zero virtuality of the quark as $M(p^2)\\propto p^2$. Our arguments follow from the constrained-instanton model of the QCD vacuum and from QCD sum rules calculations with nonlocal condensates. The discussed models also lead to analyticity of $M(p^2)$ in the vicinity of zero.
Novel zero-current-transition PWM converters
Guichao Hua; Eric X. Yang; Yimin Jiang; Fred C. Lee
1993-01-01
A new family of zero-current-transition (ZCT) pulse-width-modulated (PWM) converters are proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage\\/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches.
Novel zero-current-transition PWM converters
Guichao Hua; Eric X. Yang; Yimin Jiang; Fred C. Lee
1994-01-01
A new family of zero-current-transition (ZCT) pulsewidth-modulated (PWM) converters is proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage\\/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches.
Novel zero-voltage-transition PWM converters
Guichao Hua; Ching-Shan Leu; Yimin Jiang; Fred C. Y. Lee
1994-01-01
To date, soft-switching techniques applied to the PWM converters, with the exception of a few isolated cases, are subjected to either high switch voltage stresses or high switch current stresses, or both. A new class of zero-voltage-transition PWM converters is proposed, where both the transistor and the rectifier operate with zero-voltage switching and are subjected to minimum voltage and current
Marcelo Samuel Berman
2009-08-16
We consider the energy of the Universe, from the pseudo-tensor point of view(Berman,1981). We find zero values, when the calculations are well-done.The doubts concerning this subject are clarified, with the novel idea that the justification for the calculation lies in the association of the equivalence principle, with the nature of co-motional observers, as demanded in Cosmology. In Section 4, we give a novel calculation for the zero-total energy result.
Novel zero-voltage-transition PWM converters
Guichao Hua; Ching-Shan Leu; Fred C. Lee
1992-01-01
A class of zero voltage transition (ZVT) power converters is proposed in which both the transistor and the rectifier operate with zero voltage switching and are subjected to minimum voltage and current stresses. The boost ZVT-PWM converter is used as an example to illustrate the operation of these converters. A 300 kHz, 600 W ZVT-PWM boost, DC-DC converter, and a
Computing the zeros of periodic descriptor systems
Andras Varga; Paul Van Dooren
In this paper, we give a numerically reliable algorithm to compute the zeros of a periodic descriptor system. The algorithm is a variant of the staircase algorithm applied to the system pencil of an equivalent lifted time-invariant state-space system and extracts a low-order pencil which contains the zeros (both 6nite and in6nite) as well as the Kronecker structure of the
Scattering of internal gravity waves
Leaman Nye, Abigail
2011-04-19
Scattering of Internal Gravity Waves Abigail Leaman Nye Selwyn College A dissertation submitted to the University of Cambridge for the degree of Doctor of Philosophy April 2009 Summary Internal gravity waves play a fundamental role in the dynamics... subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate and weather predictions. Field studies report significantly enhanced measurements...
Atom interferometric gravity sensor system
Dave Brown; Lorraine Mauser; Brenton Young; Mark Kasevich; Hugh F. Rice; Vincent Benischek
2012-01-01
Real-time gravity measurements provide an accurate, high-resolution snapshot of the local gravity signature. Information developed from the gravity signature can be a significant contributor to battle space situational awareness, providing enhanced knowledge of the local operating environment and of the location of each operational participant in that environment. The Strategic Systems Programs (SSP) Navigation Branch (SP24) and Lockheed Martin, Maritime
Cascading gravity is ghost free
Rham, Claudia de [Departement de Physique Theorique, Universite de Geneve, 24 Quai E. Ansermet, CH-1211 Geneve (Switzerland); Khoury, Justin [Center for Particle Cosmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6395 (United States); Tolley, Andrew J. [Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada)
2010-06-15
We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.
Alishahiha, Mohsen; Fareghbal, Reza [School of physics, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5531, Tehran (Iran, Islamic Republic of)
2011-04-15
We study Einstein gravity in dimensions D{>=}4 modified by curvature squared at critical point where the theory contains only massless gravitons. We show that at the critical point a new mode appears leading to a logarithmic gravity in the theory. The corresponding logarithmic solution may provide a gravity description of logarithmic conformal field theories (CFT) in higher dimensions. We note also that for special values of the parameters of the theory, the model admits solutions with nonrelativistic isometries.
Primer on Gravity and Magnetics
NSDL National Science Digital Library
Richard Gibson
This web page explains the goals and benefits of studying gravity and magnetic data to understand subsurface geology of the Earth. It discusses uses of gravity and magnetic measurements in providing information about the density of rocks, and explains how these measurements are useful in exploration for oil and gas and mineral deposits. The page uses gravity and magnetic maps and as well as figures to illustrate some of the concepts of interpretation, such as amplitude, frequency and anomalies.
What measurable zero point fluctuations can(not) tell us about dark energy
Michael Doran; Joerg Jaeckel
2006-05-30
We show that laboratory experiments cannot measure the absolute value of dark energy. All known experiments rely on electromagnetic interactions. They are thus insensitive to particles and fields that interact only weakly with ordinary matter. In addition, Josephson junction experiments only measure differences in vacuum energy similar to Casimir force measurements. Gravity, however, couples to the absolute value. Finally we note that Casimir force measurements have tested zero point fluctuations up to energies of ~10 eV, well above the dark energy scale of ~0.01 eV. Hence, the proposed cut-off in the fluctuation spectrum is ruled out experimentally.
Zhu, Kehe
MAXIMAL ZERO SEQUENCES FOR FOCK SPACES KEHE ZHU ABSTRACT. A sequence Z in the complex plane C is called a zero se- quence for the Fock space Fp if there exists a function f Fp , not identically zero, such that Z is the zero set of f, counting multiplicities. We show that there exist zero sequences Z for Fp
Do cosmological perturbations have zero mean?
Armendariz-Picon, Cristian, E-mail: armen@phy.syr.edu [Department of Physics, Syracuse University, Syracuse, NY 13244-1130 (United States)
2011-03-01
A central assumption in our analysis of cosmic structure is that cosmological perturbations have a constant ensemble mean, which can be set to zero by appropriate choice of the background. This property is one of the consequences of statistical homogeneity, the invariance of correlation functions under spatial translations. In this article we explore whether cosmological perturbations indeed have zero mean, and thus test one aspect of statistical homogeneity. We carry out a classical test of the zero mean hypothesis against a class of alternatives in which primordial perturbations have inhomogeneous non-vanishing means, but homogeneous and isotropic covariances. Apart from Gaussianity, our test does not make any additional assumptions about the nature of the perturbations and is thus rather generic and model-independent. The test statistic we employ is essentially Student's t statistic, applied to appropriately masked, foreground-cleaned cosmic microwave background anisotropy maps produced by the WMAP mission. We find evidence for a non-zero mean in a particular range of multipoles, but the evidence against the zero mean hypothesis goes away when we correct for multiple testing. We also place constraints on the mean of the temperature multipoles as a function of angular scale. On angular scales smaller than four degrees, a non-zero mean has to be at least an order of magnitude smaller than the standard deviation of the temperature anisotropies.
Peter West
2014-11-04
We consider the equation of motion in the gravity sector that arises from the non-linear realisation of the semi-direct product of E11 and its first fundamental representation, denoted by l1, in four dimensions. This equation is first order in derivatives and at low levels relates the usual field of gravity to a dual gravity field. When the generalised space-time is restricted to be the usual four dimensional space-time we show that this equation does correctly describe Einstein's theory at the linearised level. We also comment on previous discussions of dual gravity.
Shan Gao
2011-07-16
The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde's example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde's argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.
A Challenge to Entropic Gravity
Jonathan J. Roveto; Gerardo Munoz
2012-01-12
In a recent publication in this journal, Erik Verlinde attempts to show that gravity should be viewed not as a fundamental force, but rather as an emergent thermodynamic phenomenon arising from an unspecified microscopic theory via equipartition and holography. This paper presents a challenge to his reformulation of gravity. A detailed examination of Verlinde's derivation leads to a number of questions that severely weaken the claim that such a theory correctly reproduces Newton's laws or Einstein gravity. In particular, we find that neither Newtonian gravity nor the Einstein equations are uniquely determined using Verlinde's postulates.
Low scale quantum gravity in gauge-Higgs unified models
Jubin Park
2015-01-19
We consider the scale at which gravity becomes strong in linearized General Relativity coupled to the gauge-Higgs unified(GHU) model. We also discuss the unitarity of S-matrix in the same framework. The Kaluza-Klein(KK) gauge bosons, KK scalars and KK fermions in the GHU models can drastically change the strong gravity scale and the unitarity violation scale. In particular we consider two models GHU_SM and GHU_MSSM which have the zero modes corresponding to the particle content of the Standard Model and the Minimal Supersymmetric Standard Model, respectively. We find that the strong gravity scale could be lowered as much as 10^13 (10^14) GeV in the GHU_SM (GHU_MSSM) for one extra dimension taking 1 TeV as the compactification scale. It is also shown that these scales are proportional to the inverse of the number of extra dimensions d. In the d=10 case, they could be lowered up to 10^5 GeV for both models. We also find that the maximum compactification scales of extra dimensions quickly converge into one special scale M_O near Planck scale or equivalently into one common radius R_0 irrespectively of d as the number of zero modes increases. It may mean that all extra dimensions emerge with the same radius near Planck scale. In addition, it is shown that the supersymmetry can help to remove the discordance between the strong gravity scale and the unitarity violation scale.
Zero bias transformation and asymptotic expansions March 3, 2009
Paris-Sud XI, Université de
Zero bias transformation and asymptotic expansions Ying Jiao March 3, 2009 Abstract We apply the zero bias transformation to deduce a recursive asymptotic expansion formula for expectation, zero bias transformation, Stein's method, asymp- totic expansions, concentration inequality 1
NASA Astrophysics Data System (ADS)
Kaifler, Bernd; Kaifler, Natalie; Dörnbrack, Andreas; Ehard, Benedikt; Rapp, Markus
2015-04-01
The international Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign was carried out in New Zealand during austral winter 2014. Its aim was to extensively study gravity waves from their sources in the troposphere, along their propagation through the atmosphere to the regions of dissipation at high altitudes. New Zealand was chosen due to its proximity to the edge of the polar vortex and its orography where strong flows excite gravity waves, making it one of the world's gravity wave hotspots. During DEEPWAVE, a comprehensive set of instruments was operated to observe gravity waves. The DLR Rayleigh/Raman lidar was set up at NIWA station in Lauder on New Zealand's South Island in June 2014. The instrumented was operated whenever weather permitted. Temperature profiles are retrieved between 22 and 80 km with 10 min temporal and 1 km vertical resolution. In order to study variations in gravity wave propagation associated with the breakdown of the polar vortex, observations were continued beyond the DEEPWAVE campaign. In total 755 operation hours during 99 nights were accumulated between June and November 2014. We present statistics of gravity wave activity and wave parameters which we derived from this extensive dataset using filtering techniques and spectral analysis. In a first step, we characterize gravity wave activity using the gravity wave potential energy density. Then we study spectral properties of the waves using two-dimensional FFT of wave-induced temperature variances. We find that in the stratosphere, low-frequency waves with periods close to the inertial period are very common. Large-amplitude waves with periods of less than two hours occur at times mainly in the mesosphere. The distribution of observed phase speeds suggests that observed waves fall into three groups: one group with mean phase speeds of -3 km/h, one group with phase speeds close to zero, and a broad background. In addition to statistics, we show case studies of selected gravity wave events.
Zero/zero rotorcraft certification issues. Volume 2: Plenary session presentations
NASA Technical Reports Server (NTRS)
Adams, Richard J.
1988-01-01
This report analyzes the Zero/Zero Rotorcraft Certification Issues from the perspectives of manufacturers, operators, researchers and the FAA. The basic premise behind this analysis is that zero/zero, or at least extremely low visibility, rotorcraft operations are feasible today from both a technological and an operational standpoint. The questions and issues that need to be resolved are: What certification requirements do we need to ensure safety. Can we develop procedures which capitalize on the performance and maneuvering capabilities unique to rotorcraft. Will extremely low visibility operations be economically feasible. This is Volume 2 of three. It presents the operator perspectives (system needs), applicable technology and zero/zero concepts developed in the first 12 months of research of this project.
Gravity Estimation from a Simulated GRACE Mission: Short vs. Long Arcs
NASA Technical Reports Server (NTRS)
Rowlands, David D.; Ray, Richard D.; Chinn, D. S.; Lemoine, F. G.; Smith, David E. (Technical Monitor)
2001-01-01
We present simulations of gravity estimation from a GRACE-like satellite mission: low-low intersatellite tracking with a precision of order 1 micron s(exp -1) yielding gravity fields of degree and order 120. We employ a unique parameterization of the intersatellite baseline vector which allows the gravity estimation to be performed (relatively) independently of the GPS (global positioning system) tracking data once sufficiently accurate orbits are obtained. This considerably simplifies data processing during the gravity estimation. During that process only certain components of the baseline parameterization need be adjusted; other components are uncorrelated with gravity and may be adopted unchanged from the initial GPS orbits. The technique is also amenable to very short arcs of data. We present comparisons of gravity estimation from 30 days of observations with arcs of length 15 minutes vs. arcs of one day. Our 'truth' field is the EGM96 (Earth Gravitational Model) model; our prior field is a degree-70 clone of EGM96, perturbed from it by amounts comparable to the standard errors of EGM96 (and identically zero for degrees 71-120). For a high inclination orbit, the short-arc analysis recovers low order gravity coefficients remarkably well, although higher order terms, especially sectorial terms, are understandably less accurate. The simulations suggest that either long or short arcs of GRACE data are likely to improve parts of the geopotential spectrum by several orders of magnitude. This is especially so for low order coefficients, which are markedly improved for all degrees through 120.
Phase transitions in warped AdS3 gravity
NASA Astrophysics Data System (ADS)
Detournay, Stéphane; Zwikel, Céline
2015-05-01
We consider asymptotically Warped AdS3 black holes in Topologically Massive Gravity. We study their thermodynamic stability and show the existence of a Hawking-Page phase transition between the black hole and thermal background phases. At zero angular potential, the latter is shown to occur at the self-dual point of the dual Warped Conformal Field Theory partition function, in analogy with the phase transition for BTZ black holes in AdS3/CFT2. We also discuss how the central and vacuum charges can be obtained from inner horizon mechanics in the presence of a gravitational anomaly.
Probing Quantum Gravity Through Exactly Soluble Midi-Superspaces I
A. Ashtekar; M. Pierri
1996-06-28
It is well-known that the Einstein-Rosen solutions to the 3+1 dimensional vacuum Einstein's equations are in one to one correspondence with solutions of 2+1 dimensional general relativity coupled to axi-symmetric, zero rest mass scalar fields. We first re-examine the quanization of this midi-superspace paying special attention to the asymptotically flat boundary conditions and to certain functional analytic subtleties associated with regularization. We then use the resulting quantum theory to analyze several conceptual and technical issues of quantum gravity.
Discrete Quantum Gravity in the Regge Calculus Formalism
Khatsymovsky, V.M. [Budker Institute of Nuclear Physics, Siberian Division, Russian Academy of Sciences, pr. Akademika Lavrent'eva 11, Novosibirsk, 630090 (Russian Federation)
2005-09-01
We discuss an approach to the discrete quantum gravity in the Regge calculus formalism that was developed in a number of our papers. The Regge calculus is general relativity for a subclass of general Riemannian manifolds called piecewise flat manifolds. The Regge calculus deals with a discrete set of variables, triangulation lengths, and contains continuous general relativity as a special limiting case where the lengths tend to zero. In our approach, the quantum length expectations are nonzero and of the order of the Plank scale, 10{sup -33} cm, implying a discrete spacetime structure on these scales.
Naked singularities are not singular in distorted gravity
NASA Astrophysics Data System (ADS)
Garattini, Remo; Majumder, Barun
2014-07-01
We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheele-DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity.
Diffraction patterns in ferrofluids: Effect of magnetic field and gravity
NASA Astrophysics Data System (ADS)
Radha, S.; Mohan, Shalini; Pai, Chintamani
2014-09-01
In this paper, we report the experimental observation of diffraction patterns in a ferrofluid comprising of Fe3O4 nanoparticles in hexane by a 10 mW He-Ne laser beam. An external dc magnetic field (0-2 kG) was applied perpendicular to the beam. The diffraction pattern showed a variation at different depths of the sample in both zero and applied magnetic field. The patterns also exhibit a change in shape and size as the external field is varied. This effect arises due to thermally induced self-diffraction under the influence of gravity and external magnetic field.
Conceptualization and design of a variable-gravity research facility
NASA Technical Reports Server (NTRS)
1987-01-01
The goal is to provide facilities for the study of the effects of variable-gravity levels in reducing the physiological stresses upon the humans of long-term stay time in zero-g. The designs studied include: twin-tethered two module system with a central despun module with docking port and winch gear; and rigid arm tube facility using shuttle external tanks. Topics examined included: despun central capsule configuration, docking clearances, EVA requirements, crew selection, crew scheduling, food supply and preparation, waste handling, leisure use, biomedical issues, and psycho-social issues.
The role of information in gravity
M. Spaans
2009-07-24
It is argued that particle-specific information on energy-momentum adjusts the strength of gravity. This form of gravity has no free parameters, preserves Einstein gravity locally and predicts 6 times stronger accelerations on galaxy scales.
The structure of local gravity theories
Maurice J. Dupre
2014-03-12
We discuss the structure of local gravity theories as resulting from the idea that locally gravity must be physically characterized by tidal acceleration, and show how this relates to both Newtonian gravity and Einstein's general relativity.
Further studies of propellant sloshing under low-gravity conditions
NASA Technical Reports Server (NTRS)
Dodge, F. T.
1971-01-01
A variational integral is formulated from Hamilton's Principle and is proved to be equivalent to the usual differential equations of low-gravity sloshing in ellipsoidal tanks. It is shown that for a zero-degree contact angle the contact line boundary condition corresponds to the stuck condition, a result that is due to the linearization of the equations and the ambiguity in the definition of the wave height at the wall. The variational integral is solved by a Rayleigh-Ritz technique. Results for slosh frequency when the free surface is not bent-over compare well with previous numerical solutions. When the free surface is bent over, however, the results for slosh frequency are considerably larger than those predicted by previous finite-difference, numerical approaches: the difference may be caused by the use of a zero degree contact angle in the present theory in contrast to the nonzero contact angle used in the numerical approaches.
Low gravity synthesis of polymers with controlled molecular configuration
NASA Technical Reports Server (NTRS)
Heimbuch, A. H.; Parker, J. A.; Schindler, A.; Olf, H. G.
1975-01-01
Heterogeneous chemical systems have been studied for the synthesis of isotactic polypropylene in order to establish baseline parameters for the reaction process and to develop sensitive and accurate methods of analysis. These parameters and analytical methods may be used to make a comparison between the polypropylene obtained at one g with that of zero g (gravity). Baseline reaction parameters have been established for the slurry (liquid monomer in heptane/solid catalyst) polymerization of propylene to yield high purity, 98% isotactic polypropylene. Kinetic data for the slurry reaction showed that a sufficient quantity of polymer for complete characterization can be produced in a reaction time of 5 min; this time is compatible with that available on a sounding rocket for a zero-g simulation experiment. The preformed (activated) catalyst was found to be more reproducible in its activity than the in situ formed catalyst.
NASA Technical Reports Server (NTRS)
Fichtl, G. H.; Holland, R. L.
1978-01-01
A stochastic model of spacecraft motion was developed based on the assumption that the net torque vector due to crew activity and rocket thruster firings is a statistically stationary Gaussian vector process. The process had zero ensemble mean value, and the components of the torque vector were mutually stochastically independent. The linearized rigid-body equations of motion were used to derive the autospectral density functions of the components of the spacecraft rotation vector. The cross-spectral density functions of the components of the rotation vector vanish for all frequencies so that the components of rotation were mutually stochastically independent. The autospectral and cross-spectral density functions of the induced gravity environment imparted to scientific apparatus rigidly attached to the spacecraft were calculated from the rotation rate spectral density functions via linearized inertial frame to body-fixed principal axis frame transformation formulae. The induced gravity process was a Gaussian one with zero mean value. Transformation formulae were used to rotate the principal axis body-fixed frame to which the rotation rate and induced gravity vector were referred to a body-fixed frame in which the components of the induced gravity vector were stochastically independent. Rice's theory of exceedances was used to calculate expected exceedance rates of the components of the rotation and induced gravity vector processes.
Three Least-Squares Minimization Approaches to Interpret Gravity Data Due to Dipping Faults
NASA Astrophysics Data System (ADS)
Abdelrahman, E. M.; Essa, K. S.
2015-02-01
We have developed three different least-squares minimization approaches to determine, successively, the depth, dip angle, and amplitude coefficient related to the thickness and density contrast of a buried dipping fault from first moving average residual gravity anomalies. By defining the zero-anomaly distance and the anomaly value at the origin of the moving average residual profile, the problem of depth determination is transformed into a constrained nonlinear gravity inversion. After estimating the depth of the fault, the dip angle is estimated by solving a nonlinear inverse problem. Finally, after estimating the depth and dip angle, the amplitude coefficient is determined using a linear equation. This method can be applied to residuals as well as to measured gravity data because it uses the moving average residual gravity anomalies to estimate the model parameters of the faulted structure. The proposed method was tested on noise-corrupted synthetic and real gravity data. In the case of the synthetic data, good results are obtained when errors are given in the zero-anomaly distance and the anomaly value at the origin, and even when the origin is determined approximately. In the case of practical data (Bouguer anomaly over Gazal fault, south Aswan, Egypt), the fault parameters obtained are in good agreement with the actual ones and with those given in the published literature.
Douglas Scott; Martin White
1995-05-22
The study of anisotropies in the Cosmic Microwave Background radiation is progressing at a phenomenal rate, both experimentally and theoretically. These anisotropies can teach us an enormous amount about the way that fluctuations were generated and the way they subsequently evolved into the clustered galaxies which are observed today. In particular, on sub-degree scales the rich structure in the anisotropy spectrum is the consequence of gravity-driven acoustic oscillations occurring before the matter in the universe became neutral. The frozen-in phases of these sound waves imprint a dependence on many cosmological parameters, that we may be on the verge of extracting.
Gravity from Quantum Information
Jae-Weon Lee; Hyeong-Chan Kim; Jungjai Lee
2013-04-13
It is suggested that the Einstein equation can be derived from Landauer's principle applied to an information erasing process at a local Rindler horizon and Jacobson's idea linking the Einstein equation with thermodynamics. When matter crosses the horizon, the information of the matter disappears and the horizon entanglement entropy increases to compensate the entropy reduction. The Einstein equation describes an information-energy relation during this process, which implies that entropic gravity is related to the quantum entanglement of the vacuum and has a quantum information theoretic origin.