Презентация на тему «Search for hypothetical corrections of Newtonian gravity at l~100nm»

Search for hypothetical corrections of Newtonian gravity at l~100nm

Ricardo S. Decca Department of Physics, IUPUI

Collaborators

Funding

Daniel L?pez Argonne National Labs Ephraim Fischbasch Purdue University Dennis E. Krausse Wabash College and Purdue University Valdimir M. Mostepanenko Noncommercial Partnership “Scientific Instruments”, Russia Galina L. Klimchitskaya North-West Technical University, Russia Ho Bun Chan University of Florida Jing Ding IUPUI Hua Xing IUPUI NSF, DOE, LANL

Jonathan L. Feng, Science 301, 795 (’03)

What is the background?

The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted)

Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances.

With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances.

Attractive force

Dominant electronic force at small (~ 1 nm) separations Non-retarded: van der Waals Retarded: Casimir

No mode restriction on the outside

2a

Yukawa-like potential

?

f1

f2

1

2

Arises from very different pictures: Compact extra-dimensions Exchange of single light (but massive, m =1/l) boson Moduli; Graviphotons; Dilatons; Hyperphotons; Axions

PRL 98, 021101 (2007)

Yukawa-like potential

Get rid of the background altogether

Arises from very different pictures: Compact extra-dimensions Exchange of light (but massive, m =1/l) boson -Moduli -Graviphotons -Dilatons -Hyperphotons -Axions

How do we establish limits?

Measure background and subtract it

Experimental setup

Dynamic measurements

Separation measurement

zg = (2389.6 ± 0.1) nm, interferometer zi = ~(10000.0 ± 0.2) absolute interferometer zo = (6960.1 ± 0.5) nm, electrostatic calibration b = (210 ± 3) mm, optical microscope Q = ~(1.000 ± 0.001) mrad

zmeas is determined using a known interaction zi, Q are measured for each position

Comparison with theory

AFM image of the Au plane

vi: Fraction of the sample at separation zi

Comparison with theory

“Casimir-less” experiments

Au

Au

Ge

Si MTO

“Casimir-less” experiments

Signal optimization: Work at wo!!! Heterodyne Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo

1 sec

10 sec

100 sec

1000 sec

z = 500 nm

“Casimir-less” experiments

Net force!

F

Signal optimization: Work at wo!!! Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo

95% confidence level

“Casimir-less” experiments

F

Background

Al2O3

Au

Au

Au

Ge

Si MTO

Motion not parallel to the axis (too small) Step (0.1 nm needed) Difference in electrostatic force (0.1 mV needed) Difference in Au coating (unlikely) Au coating not thick enough (unlikely)

What next

Two orders of magnitude improvement

Conclusions Most sensitive measurements of the Casimir Force and

Casimir Pressure Unprecedented agreement with theory First realization of a “Casimir-less” experiment Improvement of about three orders of magnitude in Yukawa-like hypothetical forces New experiment under way. Results expected by the end of the year.