  Although the Tomonaga-Luttinger liquid exhibits spin-charge separation and
the electron is not an elementary excitation of the system, nevertheless an
effective electronic dispersion may be defined by the frequency-dependent peak
in the momentum distribution curve (MDC). The MDC is defined by considering the
single hole spectral function $A^<(\vec{k},\omega)$ as a function of $\vec{k}$
at a fixed frequency $\omega$. We show the existence of a \emph{kink} in this
dispersion for the spin-rotationally invariant Tomonaga-Luttinger liquid at
finite temperature. In the repulsive regime where the charge velocity $v_{c}$
is greater than the spin velocity $v_{s}$, the low frequency effective
electronic dispersion is linear in $\vec{k}$ and follows a velocity $v_l$
between the spin and charge velocities, $v_s < v_l < v_c$. The high frequency
part (which is also linear in $\vec{k}$) disperses with the charge velocity
$v_c$. The energy scale of the crossover between the two velocities defines a
kink, $E_{\rm kink}$. In addition, the high energy dispersion extrapolates to
the Fermi energy at a wavevector $k_{ex} \ne k_F$ which is shifted from the
Fermi wavevector. The presence of such a kink is measurable with, {\em e.g.},
angle-resolved photoemission experiments, and may be used to test for the
presence of Luttinger liquid behavior in systems in which the separate
contributions from spin and charge to the MDC are not discernible due to strong
interactions or low experimental resolution.
