  In this paper, we investigate the two competing effects of strains and
magnetic fields in single-layer graphene to explore its impact on various
phenomena of quantum field theory, such as induced charge density, magnetic
catalysis, symmetry breaking, dynamical mass generation and magnetization. We
show that the interplay between strains and magnetic fields produces not only a
breaking of chiral symmetry, as it happens in QED$_{2+1}$, but also parity and
time-reversal symmetry breaking. The last two symmetry breakings are related to
the dynamical generation of a Haldane mass term. We find that it is possible to
modify the magnetization and the dynamical mass independently for each valley,
by strain and varying the external magnetic field. Furthermore, we discover
that the presence of a non-zero pseudomagnetic field, unlike the magnetic one,
allows us to observe an induced "vacuum" charge and a parity anomaly in
strained graphene. Finally, because the combined effect of real and
pseudomagnetic fields produces an induced valley polarization, the results
presented here may provide new tools to design valleytronic devices.
