To test the cosmic spatial isotropy, we use a rotatable torsion balance carrying a transversely spin-polarized ferrimagnetic Dy_{ 6}Fe_{ 23} mass. With a rotation period of one hour, the period of anisotropy signal is reduced from one sidereal day by about 24 times, and hence the 1/f noise is greatly reduced. Our present experimental results constrain the cosmic anisotropy Hamiltonian H = C_{ 1} sigma_{ 1} + C_{ 2} sigma_{ 2} + C_{ 3} sigma_{ 3} (sigma_{ 3} is in the axis of earth rotation) to (C_{ 1}^{ 2} +C_{ 2}^{ 2})^{ 1/2} = (1.8 +- 5.3) X 10^{ -21} eV and | C_{ 3} | = (1.2 +- 3.5) X 10^{ -19} eV. This improves the previous limits on (C_{ 1},C_{ 2}) by 120 times and C_{ 3} by a factor of 800.
Categories: physics.space-ph