Inflationary Gravitational Waves: Recent Developments and Next Steps
Marc Kamionkowski Johns Hopkins University - Department of Physics & Astronomy
PIRSA:14060024
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New methods for detecting short-range forces and gravitational waves using resonant sensors
Andrew Geraci University of Nevada Reno
PIRSA:14060019The Exact Renormalization Group and Higher Spin Holography.
Rob Leigh University of Illinois Urbana-Champaign
Probing Gravity and Small Forces with Torsion Balances
Blayne Heckel University of Washington
PIRSA:14060018Resonant Detection of Short-Range Gravitational Forces
Eli Levenson-Falk University of Southern California
PIRSA:14060046Fundamental physics with atom interferometry
Jason Hogan Stanford Law School - The Bill Lane Centre for the American West
PIRSA:14060016Precision gravity measurements with cold atom interferometry
Guglielmo Tino National Institute for Nuclear Physics
PIRSA:14060015Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy
Geoff Blewitt University of Nevada Reno
PIRSA:14060014
Inflationary Gravitational Waves: Recent Developments and Next Steps
Marc Kamionkowski Johns Hopkins University - Department of Physics & Astronomy
PIRSA:14060024The recently reported evidence for the cosmic microwave background signature of inflationary gravitational waves is very tantalizing. I will discuss how the measurement is done, the evidence presented by BICEP2, the interpretation, and some of the criticisms of the arguments presented by BICEP2 that the signal is not dust-dominated. I will then review next steps to be taken with future CMB experiments and with galaxy surveys.Precision Spectroscopy of Atomic Lithium
Jason Stalnaker Oberlin College
PIRSA:14060022The simplicity of the atomic structure of lithium has long made it a system of theoretical interest. With the development of stabilized optical frequency combs, it is possible to achieve experimental accuracies that provide significant tests of atomic theory calculations as well as a window into nuclear structure. I will discuss an ongoing experimental effort at Oberlin College to measure the energy levels of lithium using a stabilized optical frequency comb.A quantum network of clocks
Mikhail Lukin Harvard University
PIRSA:14060021By combining precision metrology and quantum networks, we describe a quantum, cooperative protocol for the operation of a network consisting of geographically remote optical atomic clocks. Using non-local entangled states, we demonstrate an optimal utilization of the global network resources, and show that such a network can be operated near the fundamental limit set by quantum theory yielding an ultra-precise clock signal. Besides serving as a real-time clock for the international time scale, the proposed quantum network also represents a large-scale quantum sensor that can be used to probe the fundamen- tal laws of physics, including relativity and connections between space-time and quantum physics. Prospects for realization of such networks will be discussed.Dark Energy and Testing Gravity
Raman Sundrum University of Maryland, College Park
PIRSA:14060020I will review why the mild acceleration of the Universe poses a major puzzle, the Cosmological Constant Problem, for the connection between gravity and matter, suggesting a possible breakdown in the standard general relativistic and field theoretic description. Thus far theorists have failed to provide any very concrete and testable resolution. I will however discuss some simple theoretical ideas that suggest directions for experiments to lead the way.New methods for detecting short-range forces and gravitational waves using resonant sensors
Andrew Geraci University of Nevada Reno
PIRSA:14060019High-Q resonant sensors enable ultra-sensitive force and field detection. In this talk I will describe three applications of these sensors in searches for new physics. First I will discuss our experiment which uses laser-cooled optically trapped silica microspheres to search for violations of the gravitational inverse square law at micron distances [1]. I will explain how similar sensors could be used for gravitational wave detection at high frequencies [2]. Finally I will describe a new method for detecting short-range spin-dependent forces from axion-like particles based on nuclear magnetic resonance in hyperpolarized Helium-3. The method can potentially improve previous experimental bounds by several orders of magnitude and can probe deep into the theoretically interesting regime for the QCD axion [3]. [1] A.Geraci, S. Papp, and J. Kitching, Phys. Rev. Lett. 105, 101101 (2010), [2] A. Arvanitaki and A. Geraci, Phys. Rev. Lett. 110, 071105 (2013), [3] A. Arvanitaki and A. Geraci, arxiv: 1403.1290 (2014).The Exact Renormalization Group and Higher Spin Holography.
Rob Leigh University of Illinois Urbana-Champaign
Probing Gravity and Small Forces with Torsion Balances
Blayne Heckel University of Washington
PIRSA:14060018The EotWash group at the University of Washington has developed a set of torsion balance
instruments to probe the properties of gravity and to search for new weak forces. Current efforts
focus on improved tests of the principle of equivalence, the inverse square law at short distances,
and spin-coupled interactions. These experiments and prospects for the future will be discussed.
Resonant Detection of Short-Range Gravitational Forces
Eli Levenson-Falk University of Southern California
PIRSA:14060046Some theories predict a short-range component to the gravitational force, typically modeled as a Yukawa modification of the gravitational potential. This force is usually detected by measuring the motion of a mechanical oscillator driven by an external mass. In this talk I will discuss such an apparatus optimized for use in the 10-100 micron distance range. The setup consists of a cantilever-style silicon nitride oscillator suspended above a rotating drive mass. Periodic density variations in the drive mass cause an oscillatory gravitational force on the cantilever, whose position is read out using optical interferometry. In order to drive the cantilever precisely on resonance, it must have a broad resonant peak; however, lower quality factors reduce force sensitivity by reducing the amplitude of oscillation for a given drive force. We solve this problem by implementing an effective damping on the oscillator by use of optical feedback. I will discuss further applications of this feedback technique, as well as improvements to the apparatus and future experiments.f(R) Gravity and Cosmology
Valerio Faraoni Bishop's University
PIRSA:14060045A popular alternative to dark energy in explaining the current acceleration of the universe discovered with type Ia supernovae is modifying gravity at cosmological scales. But this is risky: even when everything is well for cosmology, other fundamental and experimental aspects of gravity must be checked in order for the theory to be viable. The successes of modified gravity and its challenges, which have generated a large body of literature in the past ten years, will be reviewed.Fundamental physics with atom interferometry
Jason Hogan Stanford Law School - The Bill Lane Centre for the American West
PIRSA:14060016Precision atom interferometry is poised to become a powerful tool for discovery in fundamental physics. Towards this end, I will describe recent, record-breaking atom interferometry experiments performed in a 10 meter drop tower that demonstrate long-lived quantum superposition states with macroscopic spatial separations. The potential of this type of sensor is only beginning to be realized, and the ongoing march toward higher sensitivity will enable a diverse science impact, including new limits on the equivalence principle, probes of quantum mechanics, and detection of gravitational waves. Gravitational wave astronomy is particularly compelling since it opens up a new window into the universe, collecting information about astrophysical systems and cosmology that is difficult or impossible to acquire by other methods. Atom interferometric gravitational wave detection offers a number of advantages over traditional approaches, including simplified detector geometries, access to conventionally inaccessible frequency ranges, and substantially reduced antenna baselines.Precision gravity measurements with cold atom interferometry
Guglielmo Tino National Institute for Nuclear Physics
PIRSA:14060015I will discuss experiments we are conducting for precision tests of gravitational physics using cold atom interferometry. In particular, I will report on the measurement of the gravitational constant G with a Rb Raman interferometer, and on experiments based on Bloch oscillations of Sr atoms confined in an optical lattice for gravity measurements at small spatial scales and for testing Einstein equivalence principle.Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy
Geoff Blewitt University of Nevada Reno
PIRSA:14060014Satellite geodesy uses the timing of photons from satellites to determine the Earth’s time varying shape, gravity field, and orientation in space, with accuracies of <1 part per billion, or millimeters at the Earth’s surface, and centimeters at satellite altitude. Implicit in mm-level GPS positioning is the modeling of widely separated atomic clocks with sub-ns precision. The precise monitoring of the relative timing phases between widely separated atomic clocks forms the metrological basis of a recently proposed approach to detect topological dark matter of a type that affects fundamental constants. Relative clock time can be updated as often as every second using the current global network of geodetic GPS stations that record data at that rate, though many more geodetic GPS stations record data every 30 seconds. Thus GPS could be used as the world’s largest dark matter detector, potentially sensitive to dark matter structures sweeping through the entire system >100 seconds, corresponding to speeds <500 km s¬-1 relative to the solar system. Here it is shown that relative timing phases can be determined to ~0.2 ns between the global network of atomic clocks at many geodetic GPS stations on the Earth’s surface separated as far as ~12,000 km, plus those aboard the 30 GPS satellites separated as far as ~50,000 km. Available atomic clock types include caesium (Cs), rubidium (Rb), and (on the ground) hydrogen maser (Hm). Achieving sub-ns relative timing precision requires (1) dual-frequency carrier phase data measured at the few mm level, (2) rigorous modeling of many aspects of the Earth system and GPS satellite dynamics, and (3) stochastic estimation of biases in the system. For example, solar radiation pressure from momentum exchange with photons hitting the satellites perturbs orbits at the few-meter level. Imperfect modeling, such as knowledge of the satellite attitude, requires us to estimate orbit acceleration biases as they slowly vary in time. For mm-level positioning applications, clock phases are considered to be unknown biases to be estimated as a white noise process, that is, estimated independently at every data epoch without constraint. By virtue of the common view of satellites simultaneously by multiple ground stations, relative clock time can be determined between all clocks in the entire satellite-ground system by estimating all biases in a global inversion. Since the timing phase between Hm clocks can be accurately extrapolated forward in time, they set the standard by which upper limits can be set on the precision of timing at any specific instant. As a feasibility study, a custom analysis of original raw GPS phase data was designed using the GIPSY OASIS II software (from NASA JPL), processing data from ~40 ground stations of various atomic clock type. An analysis of data from GPS stations that are positioned at the few-millimeter level every day indicates that Hm clock time is determined at to ~0.2 ns. Since the smoothness of Hm clocks is not assumed anywhere in the modeling, and that station clock type has no influence on positioning precision, one can infer that timing at the 0.2 ns level is also the case for less predictable atomic clocks such as Rb and Cs, thus providing a window into possibly different coupling of dark matter with different clock types.