  We present the results of our ALMA Cycle 0 observations, using HCN/HCO+/HNC
J=4-3 lines, of six nearby luminous infrared galaxies with various energetic
contributions from active galactic nuclei (AGNs) estimated from previous
infrared spectroscopy. These lines are very effective for probing the physical
properties of high-density molecular gas around the hidden energy sources in
the nuclear regions of these galaxies. We find that HCN to HCO+ J=4-3 flux
ratios tend to be higher in AGN-important galaxies than in starburst-dominated
regions, as was seen at the J=1-0 transition, while there is no clear
difference in the HCN-to-HNC J=4-3 flux ratios among observed sources. A galaxy
with a starburst-type infrared spectral shape and very large molecular line
widths shows a high HCN-to-HCO+ J=4-3 flux ratio, which could be due to
turbulence-induced heating. We propose that enhanced HCN J=4-3 emission
relative to HCO+ J=4-3 could be used to detect more energetic activity than
normal starbursts, including deeply buried AGNs, in dusty galaxy populations.
