**Big-Bang
Nucleosynthesis**

Alain Coc

CSNSM, France

Primordial
nucleosynthesis
(or BBN) is one of the three observational evidences for the
Big-Bang model. There
is indeed a good
overall agreement between primordial abundances of D, ^{3}He,
^{4}He
and^{ 7}Li either deduced from observation or primordial
nucleosynthesis
calculations. However,
there remains a
tantalizing discrepancy of a factor of 3-5 between the
primordial ^{7}Li
abundances either calculated or deduced from observations. Solutions to this
problem have been proposed,
involving non standard models of the Big-Bang or stellar
physics, but first,
possible nuclear physics solutions have to be investigated. I will discuss the
following topics.

Nuclear
reactions,
candidates for the destruction of ^{7}Be/^{7}Li,
have
been proposed

and
nuclear
physics experiments have been (or are being) conducted to
determine their
cross-sections.

Particle
physics
solutions for reducing the ^{7}Li abundance include
free
thermal neutron injection during BBN, via decays or
annihilations of dark
matter particles.

CNO
production
in BBN could affect the evolution of the very first stars but
its calculation
relies on hundreds of thermonuclear reaction rates including
many for which
very little experimental data is available. We extended our
network to >400
reacions and pointed out the few uncertain reaction rates that
can have a
significant impact on BBN CNO production [2].

Testing
the
constancy of fundamental constants one actually performs a test
of General
Relativity, that can be extended on astrophysical and
cosmological scales. In
this context, we explore ways to reduce ^{7}Li
production [3,4] and
bridge the "A=8 gap" and produce excess CNO [4].

[1]
D.
V'asquez, A. Belikov, A. Coc, J. Silk and E. Vangioni,
submitted.

[2]
A. Coc, S.
Goriely, Y. Xu, M. Saimpert and E. Vangioni,
Astrophys. J., **744
**(2012)
158.

[3]
A. Coc, N.
Nunes, K. Olive, J.-P. Uzan and E. Vangioni, Phys. Rev. D**76** (2007) 023511.

[4]
A. Coc, P.
Descouvemont, K. Olive, J.-P. Uzan and E. Vangioni, in
preparation.