# Experimental limits on anisotropies in the $e/m_{e}$ ratio

Currently the charge-to-mass ratio of the electron is known to 10 orders of magnitude.

However, i'm curious if:

1. Are there any experiments trying to bound the anisotropy of this ratio for different directions of space? Over what time does the data needs to be averaged to get to our current ten-figure precision? Less than a day? Less than a second? Less than a month?

2. Does an spatial anisotropy (or an spatial inhomogeneity) of this ratio break Poincare symmetry, or can that be restored with replacing the mass scalar with a tensor object? Also, what theoretical ideas explicitly disallow a non-scalar fundamental mass? What about a non-scalar electromagnetic charge?

3. Does mass spectroscopic experimental data bound any anisotropic variations? Do we have any measurements of this ratio on small cavities where van der waals forces are dominant?

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How would You define that "directions"? Up/down east/west? In plane of ecliptic, orthogonal to ecliptic? or would You prefer plane of our galaxy as a reference? –  Georg Apr 3 '11 at 12:30
i'm not sure, but i would expect any anisotropy to manifest by measuring variations at either a 24-hour or 1-year periods in 3 fixed axis directions at earth –  lurscher Apr 3 '11 at 12:36
Why are you asking this question? You are not giving enough input, anyway. Anisotropy versus what? the earth? the sun? the direction of motion? The very great accuracy of the measurement gives an indication that even if an anisotropy existed with respect to the direction of motion it would be within the errors of the measurements, or at least a factor of ten to the error of the measurements. Otherwise it would have been detected. If it is a gravitational space type of question new experiments would have to be planned, but for what reason? Which theory is predicting anisotropy? –  anna v Apr 3 '11 at 12:39
@anna, no theory that i'm aware right now, but wondering how sure are we (quantitatively, and theoretically) that mass and charge are scalar constants –  lurscher Apr 3 '11 at 12:43
@Time frames are small. The ones in magnetic fields measure the radius of the circle and the magnetic field, however long that takes it is small because we are talking of ev electrons at least, quite fast. Less than a microsecond. Ditto for the Zeeman effect . There are many experiments in different labs at different times. A measurable space anisotropy would have given inconsistent results between different measurements. So any anisotropy, if it exists, is within errors. –  anna v Apr 3 '11 at 13:20