  The scattering picture of electron transport in mesoscopic conductors shows
that fluctuations of the current reveal additional information on the
scattering mechanism not available through the conductance alone. The
electronic fluctuations are coupled to the electromagnetic field and a junction
at finite bias or temperature will emit radiation. The nonsymmetrized
current-current correlators characterize the emission and absorption spectrum.
Recent interest is focused on the so-called delta-T noise, which is the
nonequilibrium noise caused by a temperature difference between the terminals.
Here, we generalize the notion of delta-T noise to the nonsymmetrized
current-current correlator at finite frequencies. We investigate the spectral
density for energy-independent scattering and for a resonant level as an
example of energy-dependent scattering. We find that a temperature difference
$\Delta T$ leads to a partial reduction of the noise for certain frequency
ranges. This is a consequence of temperature broadening in combination with a
frequency shift of the involved Fermi distributions. In the case of
energy-independent scattering, the lowest order is a quadratic $\propto (\Delta
T)^2$ correction of the thermal-like noise spectrum. For the resonance,
additional contributions to the delta-T noise spectrum arise that are $\propto
\Delta T$ to the lowest order.
