Inflaton

The basic model of inflation proceeds in three phases:[4]

• Expanding vacuum state with high potential energy
• Phase transition to true vacuum
• Slow roll and reheating

Just like every other quantum field, excitations of the inflaton field are expected to be quantized. The field quanta of the inflaton field are known as inflatons. Depending on the modeled potential energy density, the inflaton field's ground state might, or might not, be zero.

The term inflaton follows the typical style of other quantum particles’ names – such as photon, gluon, boson, and fermion – deriving from the word inflation. The term was first used in a paper by Nanopoulos, Olive, and Srednicki (1983).[5] The nature of the inflaton field is currently not known. One of the obstacles for narrowing its properties is that current quantum theory is not able to correctly predict the observed vacuum energy, based on the particle content of a chosen theory (see vacuum catastrophe).

Atkins (2012) suggested that it is possible that no new field is necessary – that a modified version of the Higgs field could function as an inflaton.[6]

Non-minimally coupled inflation is an inflationary model in which the constant which couples gravity to the inflaton field is not small. The coupling constant is usually represented by ${\displaystyle \xi }$ (letter xi), which features in the action (constructed by modifying the Einstein–Hilbert action):[7]^: 1–2

${\displaystyle S=\int d^{4}x{\sqrt {-g}}\left[{\tfrac {1}{2}}m_{P}^{2}R-{\tfrac {1}{2}}\partial ^{\mu }\phi \partial _{\mu }\phi -V(\phi )-{\tfrac {1}{2}}\xi R\phi ^{2}\right]}$,

with ${\displaystyle \xi }$ representing the strength of the interaction between ${\displaystyle R}$ and ${\displaystyle \phi }$, which respectively relate to the curvature of space and the magnitude of the inflaton field.