Talks

11545 - 11556 of 20132 Results

Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy

Geoff Blewitt University of Nevada Reno

June 17, 2014

PIRSA:14060014
Free Discussion

June 16, 2014

PIRSA:14060013
Spectroscopic constrains on variation of fundamental constants in astrophysics.

Mikhail Kozlov University of Turku

June 16, 2014

PIRSA:14060012
Time and frequency metrology at NIST

Jeff Sherman National Institute of Standards and Technology

June 16, 2014

PIRSA:14060011
Frequency comparison of cryogenic optical lattice clocks

Hidetoshi Katori University of Tokyo

June 16, 2014

PIRSA:14060010
Zen and the art of atomic time-keeping (Tutorial on atomic clocks for particle theorists)

Andrei Derevianko University of Nevada Reno

June 16, 2014

PIRSA:14060009
Atomic Clocks and Tests of Fundamental Physics

Ekkehard Peik Physikalisch-Technische Bundesanstalt (PTB)

June 16, 2014

PIRSA:14060008
Introduction, Scope and goals of the workshop, Open questions in the field

Asimina Arvanitaki Perimeter Institute

Derek Jackson Kimball California State University, East Bay

Maxim Pospelov University of Minnesota

Dmitry Budker University of California, Berkeley

June 16, 2014

PIRSA:14050149
Welcome

June 16, 2014

PIRSA:14060007
What Can We Learn from Precision Higgs

Maxim Perelstein Cornell University

June 13, 2014

PIRSA:14060003

High Energy Physics
Inflation, Variable Speed of Light and BICEP2

John Moffat Perimeter Institute for Theoretical Physics

June 12, 2014

PIRSA:14060044

Astrophysics
Sequential growth dynamics and quantum random walks

David Meyer University of California, San Diego

June 11, 2014

PIRSA:14060042

Mathematical Physics

Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy

Geoff Blewitt University of Nevada Reno

June 17, 2014

PIRSA:14060014

Satellite 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.
Free Discussion

June 16, 2014

PIRSA:14060013
Spectroscopic constrains on variation of fundamental constants in astrophysics.

Mikhail Kozlov University of Turku

June 16, 2014

PIRSA:14060012

I will discuss present limits on the variation of the fine structure constant and the electron to proton mass ratio from the astrophysical data on the spectra from the interstellar gas medium. The emphasis will be made on the infrared and microwave spectra. Such spectra may be 2 - 3 orders of magnitude more sensitive to the variation of constants than optical spectra.
Time and frequency metrology at NIST

Jeff Sherman National Institute of Standards and Technology

June 16, 2014

PIRSA:14060011

Official U.S. time is currently realized by an ensemble of commercial cesium-beam atomic clocks and hydrogen masers. Cesium-fountain devices presently serve as ultimate frequency references and help to define the SI second. The present quandary is: these microwave-based standards are rapidly becoming outmatched by new optical atomic frequency references---by a factor of 1,000 in stability, and perhaps a factor of 100 in accuracy. I will survey the ongoing optical atomic clock projects at NIST and highlight related work in optical time and frequency measurement and transfer.
Frequency comparison of cryogenic optical lattice clocks

Hidetoshi Katori University of Tokyo

June 16, 2014

PIRSA:14060010

We report frequency comparison of two Sr optical lattice clocks operated at cryogenic temperature to dramatically reduce blackbody radiation shift. After 11 measurements performed over a month, the two cryo-clocks agree to within (-1.1±1.6)×〖10〗^(-18).
Current status of a frequency ratio measurement of Hg/Sr clocks and a remote comparison of cryo-clocks located at Riken and University of Tokyo will be mentioned.
Zen and the art of atomic time-keeping (Tutorial on atomic clocks for particle theorists)

Andrei Derevianko University of Nevada Reno

June 16, 2014

PIRSA:14060009
Atomic Clocks and Tests of Fundamental Physics

Ekkehard Peik Physikalisch-Technische Bundesanstalt (PTB)

June 16, 2014

PIRSA:14060008

The precision of atomic clocks continues to improve at a rapid pace: While caesium clocks now reach relative systematic uncertainties of a few 10-16, several optical clocks based on different atomic systems are now reported with uncertainties in the 10-18 range. This variety of precise clocks will allow for improved tests of fundamental physics, especially quantitative tests of relativity and searches for variations of constants. Laser-cooled and trapped ions permit the study of strongly forbidden transitions with extremely small natural linewidths and long coherence times. The frequency of the electric octupole transition S1/2 - F7/2 at 467 nm in 171Yb+ with a natural linewidth in the nHz range is remarkably insensitive against external electric and magnetic fields. We evaluate the systematic uncertainty of a frequency standard that is based on this transition as 4*10-18 at present. An even better isolation from external perturbations can be expected for the nuclear transition in 229Th3+ at about 160 nm with an expected linewidth in the mHz range. In order to excite the so far only indirectly observed nuclear transition using electronic bridge processes, we investigate the dense electronic level structure of Th+. Both transitions, in Yb+ and 229Th, are predicted to be highly sensitive to changes in the fine structure constant. I will give an update on limits on variations of constants as obtained from atomic clock comparisons.
Introduction, Scope and goals of the workshop, Open questions in the field

Asimina Arvanitaki Perimeter Institute

Derek Jackson Kimball California State University, East Bay

Maxim Pospelov University of Minnesota

Dmitry Budker University of California, Berkeley

June 16, 2014

PIRSA:14050149
Welcome

June 16, 2014

PIRSA:14060007
What Can We Learn from Precision Higgs

Maxim Perelstein Cornell University

June 13, 2014

PIRSA:14060003

High Energy Physics

In the coming years, LHC experiments will measure Higgs properties, such as its couplings, with increasing precision. Electron-positron Higgs factories, such as the ILC or TLEP, would be able to achieve even better precision. In this talk, I will discuss some of the physics questions that can be addressed by a precision Higgs coupling measurement program. First, the issue of naturalness of the electroweak scale can be addressed in a robust, model-independent manner. Second, the possibility of a first-order electroweak phase transition can be definitively probed, testing one of the necessary conditions of electroweak baryogenesis scenario.
Inflation, Variable Speed of Light and BICEP2

John Moffat Perimeter Institute for Theoretical Physics

June 12, 2014

PIRSA:14060044

Astrophysics

A variable speed of light (VSL) cosmology is developed with a spontaneous breaking of Lorentz invariance in the early universe. A non-minimal electromagnetic coupling to curvature and the resulting quantum electrodynamic vacuum polarization dispersive medium can produce c >> c0 in the early universe, where c0 is the measured speed of light today. Higher derivative curvature contributions to the effective gravitational action and quantum gravity vacuum polarization can produce a dispersive medium and a large increase in the speed of gravitational waves cg >> cg0 in the early universe, where cg0 is the speed of gravitational waves today. The initial value problems of cosmology are solved: the horizon and flatness problems. The model predicts primordial scalar and tensor fluctuation spectral indices ns=0.96 and nt=- 0.04, respectively. The BICEP2 observation of r=0.2 yields r/nt=-5 which is close to the single-field inflationary consistency condition r/nt=-8.
Sequential growth dynamics and quantum random walks

David Meyer University of California, San Diego

June 11, 2014

PIRSA:14060042

Mathematical Physics

Rideout and Sorkin proposed a classical dynamics for causal sets based upon a sequential growth model. Comparing it with models for sequential growth in other systems, and with the dual goals of generating manifold-like causal sets and finding a quantum dynamics for them, we propose some modifications to their model. The resulting, admittedly speculative, proposal is a type of quantum random walk. We explore its properties in some simple cases.

Title	Date	Collection	Type	Info
Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy	2014‑06‑17	New ideas in low-energy tests of fundamental physics	Conference	View details
Free Discussion	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Spectroscopic constrains on variation of fundamental constants in astrophysics.	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Time and frequency metrology at NIST	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Frequency comparison of cryogenic optical lattice clocks	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Zen and the art of atomic time-keeping (Tutorial on atomic clocks for particle theorists)	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Atomic Clocks and Tests of Fundamental Physics	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Introduction, Scope and goals of the workshop, Open questions in the field	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
Welcome	2014‑06‑16	New ideas in low-energy tests of fundamental physics	Conference	View details
What Can We Learn from Precision Higgs	2014‑06‑13	Particle Physics	Scientific Series	View details
Inflation, Variable Speed of Light and BICEP2	2014‑06‑12	Cosmology and Gravitation	Scientific Series	View details
Sequential growth dynamics and quantum random walks	2014‑06‑11	Colloquium	Scientific Series	View details

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Format results

Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy

Free Discussion

Spectroscopic constrains on variation of fundamental constants in astrophysics.

Time and frequency metrology at NIST

Frequency comparison of cryogenic optical lattice clocks

Zen and the art of atomic time-keeping (Tutorial on atomic clocks for particle theorists)

Atomic Clocks and Tests of Fundamental Physics

Introduction, Scope and goals of the workshop, Open questions in the field

Welcome

What Can We Learn from Precision Higgs

Inflation, Variable Speed of Light and BICEP2

Sequential growth dynamics and quantum random walks

Atomic Clocks Monitored to 0.2 ns using Satellite Geodesy

Free Discussion

Spectroscopic constrains on variation of fundamental constants in astrophysics.

Time and frequency metrology at NIST

Frequency comparison of cryogenic optical lattice clocks

Zen and the art of atomic time-keeping (Tutorial on atomic clocks for particle theorists)

Atomic Clocks and Tests of Fundamental Physics

Introduction, Scope and goals of the workshop, Open questions in the field

Welcome

What Can We Learn from Precision Higgs

Inflation, Variable Speed of Light and BICEP2

Sequential growth dynamics and quantum random walks