  GRS 1734-292 is a radio-quiet galaxy, exhibiting neither intense starburst
nor jet activities. However, Fermi-LAT detected this object in the GeV band.
The origin of non-thermal activity in this Seyfert galaxy is an intriguing
question. We report Atacama Large Millimeter/submillimeter Array (ALMA)
observations of GRS 1734-292 at frequencies of 97.5, 145, and 225 GHz. These
observations confirmed the millimeter excess within the central <100 pc region
and its time variability based on two separate observations conducted four days
apart. The timescale of variability aligns with the light crossing time for a
compact source smaller than <100 Schwarzschild radius. If we take into account
the power-law synchrotron emission originating from the corona (i.e., the hot
plasma located above the accretion disk), the millimeter spectrum indicates the
coronal magnetic field of ~10 G and the size of ~10 Schwarzschild radius. An
alternative explanation for this millimeter emission could be synchrotron and
free-free emission from disk winds (i.e., fast wide-opening angle outflows from
the disk) with the size of ~10 pc, although it may be difficult to explain the
fast variability. Future millimeter observations with higher resolution
(~0.01") will enable the differentiation between these two scenarios. Such
observations will provide insights into the acceleration sites of high-energy
particles at the core of active galactic nuclei.
