Improved tests of local position invariance using 87Rb and 133Cs fountains.

Area of Science:

• Atomic physics
• Fundamental physics
• Metrology

Background:

• Local position invariance is a fundamental principle in physics.
• Atomic clocks offer high precision for testing fundamental physics.
• Previous studies have constrained variations in fundamental constants.

Purpose of the Study:

• To test local position invariance using atomic fountain clocks.
• To set stringent limits on the variation of the Rb/Cs hyperfine frequency ratio over time.
• To establish the first limit on the variation of this ratio with gravitational potential.

Main Methods:

• Utilized laser-cooled atomic fountain clocks with 133Cs and 87Rb.
• Measured the ratio of ground state hyperfine frequencies over 14 years.
• Analyzed frequency variations with respect to time and gravitational potential.

Main Results:

• Established a stringent limit on the temporal variation of the Rb/Cs frequency ratio: d ln(ν(Rb)/ν(Cs))/dt=(-1.39±0.91)×10(-16) yr(-1).
• Set the first limit on the fractional variation with gravitational potential: c(2)d ln(ν(Rb)/ν(Cs))/dU=(0.11±1.04)×10(-6).
• These limits constrain variations in the fine-structure constant and light quark mass.

Conclusions:

• The study provides strong evidence supporting local position invariance.
• The results significantly improve previous constraints on the variation of fundamental constants.
• This work offers a new, stringent differential redshift test.