  Type Ia supernovae (SNe Ia) are important cosmological tools, probes of
binary star evolution, and contributors to cosmic metal enrichment; yet, a
definitive understanding of the binary star systems that produce them remains
elusive. In this work we present early-time (first observation within 10 days
post-explosion) radio observations of six nearby (within 40 Mpc) SNe Ia taken
by the Jansky Very Large Array, which are used to constrain the presence of
synchrotron emission from the interaction between ejecta and circumstellar
material (CSM). The two motivations for these early-time observations are (1)
to constrain the presence of low-density winds and (2) to provide an additional
avenue of investigation for those SNe Ia observed to have early-time optical/UV
excesses that may be due to CSM interaction. We detect no radio emission from
any of our targets. Toward our first aim, these non-detections further increase
the sample of SNe Ia that rule out winds from symbiotic binaries and strongly
accreting white dwarfs. For the second aim, we present a radiation
hydrodynamics simulation to explore radio emission from an SN Ia interacting
with a compact shell of CSM, and find that relativistic electrons cannot
survive to produce radio emission despite the rapid expansion of the shocked
shell after shock breakout. The effects of model assumptions are discussed for
both the wind and compact shell conclusions.
