Under the standard model extension (SME) framework, Lorentz invariance is tested in five binary pulsars: PSR J0737-3039, PSR B 1534+12, PSR J1756-2251, PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we obtain the constraints on a dimensionless combination of SME parameters that is sen- sitive to timing observations. The results imply no evidence for the break of Lorentz invariance at the 10-l level, one order of magnitude larger than the previous estima- tion.
As an extension of the"teleparallel"equivalent of general relativity,f(T)gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f(T)gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f(T)gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f(T)gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f(T)gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.