  We have studied how the equation of state of thermal QCD with two light
flavours is modified in strong magnetic field by calculating the thermodynamic
observables of hot QCD matter up to one-loop, where the magnetic field affects
mainly the quark contribution and the gluonic part is largely unaffected except
for the softening of the screening mass due to the strong magnetic field. To
begin with the effect of magnetic field on the thermodynamics, we have first
calculated the pressure of a thermal QCD medium in strong magnetic field limit
(SML), where the pressure at fixed temperature increases with the magnetic
field faster than the increase with the temperature at constant magnetic field.
This can be envisaged from the dominant scale of thermal medium in SML, which
is the magnetic field, like the temperature in thermal medium in absence of
strong magnetic field. Thus although the presence of strong magnetic field
makes the pressure of hot QCD medium harder but the increase of pressure with
respect to the temperature becomes less steeper. Corroborated to the above
observations, the entropy density is found to decrease with the temperature in
the ambience of strong magnetic field which resonates with the fact that the
strong magnetic field restricts the dynamics of quarks in two dimensions, hence
the phase space gets squeezed resulting the reduction of number of microstates.
Moreover the energy density is seen to decrease and the speed of sound of
thermal QCD medium is increased in the presence of strong magnetic field. These
crucial findings in strong magnetic field could have phenomenological
implications in heavy ion collisions because the expansion dynamics of the
medium produced in noncentral ultrarelativistic heavy ion collisions is
effectively controlled by both the energy density and the speed of sound.
