Varying constants, Gravitation and Cosmology

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. It is thus of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We thus detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, Solar system observations, meteorites dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.Comment: 145 pages, 10 figures, Review for Living Reviews in Relativit

The new isotope 208Th

The new neutron-deficient isotope 208Th was produced in the complete-fusion reaction 64Ni + 147Sm → 208Th + 3n. Evaporation residues were separated in-flight by the velocity filter SHIP and subsequently identified on the basis of energy-, position- and time-correlated alpha-decay chains. The measured alpha-decay energy and half-life value of 208Th are 8044(30) keV and 1.7 (^{+1.7} _{−0.6}) ms, respectively. Improved data on the alpha-decay of 209Th, 210Th, 212Th and 208Ra were obtained using complete-fusion reactions of 64Ni with 147Sm, 150Sm, and 152Sm targets.status: publishe

Decay of the 9/2- isomer in 181Tl and mass determination of low-lying states in 181Tl, 177Au and 173Ir

A detailed spectroscopic study of the neutron-deficient isotope 181Tl and the daughter of its α decay, 177Au, has been performed in the complete fusion reaction 40Ca + 144Sm → 184Pb∗ at the velocity filter SHIP (GSI). The mass excess, excitation energy, and decay scheme of the isomeric 1.40(3) ms, 9/2− intruder state in 181Tl have been established for the first time. These results solve a long-standing puzzle of the unrealistically large reduced α-decay width of this isomer. Based on this, the previously unknown masses of the long-lived isomeric states in 177Au and 173Ir have been derived. In turn, it now allows the excitation energies of previously identified bands in 177Au and 173Ir to be deduced and compared with theoretical predictions. First measurements of α-decay branching ratios for 181Tlm and 177Aum,g are also reported.status: publishe

Identification and decay of the 0.48ms 13/2+ isomer in 181Hg

A new isomer with a half-life of 0.48(2) ms was identified in the nuclide 181Hg, which was produced in the complete fusion reaction 40Ca + 144Sm → 184Pb* at the velocity filter SHIP (GSI, Darmstadt). The isomeric state was tentatively assigned a spin-parity of 13/2+. We propose that this isomer de-excites by a yet unobserved low-energy, strongly converted gamma-ray transition, followed by a newly identified cascade composed of a 90.3 keV M1 and a 71.4 keV E2 gamma-ray transition.status: publishe