Standard Model Mass Spectrum in Inflationary Universe

TL;DR

The paper investigates how the Standard Model mass spectrum is modified during inflation through quantum corrections, and examines the observable imprints of these corrections in the squeezed limit of primordial non-Gaussianity. It develops and applies a Euclidean de Sitter framework to compute 1-loop mass corrections for spin-0, spin-1/2, and spin-1 fields, revealing that scalar and gauge sectors can acquire masses of order the Hubble scale $H$, while massless fermions can remain massless in certain regimes. The analysis covers both non-Higgs and Higgs inflation, deriving how the Higgs background and inflaton couplings reshape the SM spectrum, and it provides explicit expressions for the Higgs, gauge boson, and fermion masses, as well as the corresponding nonlocal bispectrum signals from SM loops. The results offer a blueprint for distinguishing Higgs-inflation scenarios via SM “fingerprints” in primordial non-Gaussianities, and they highlight observational prospects and theoretical caveats related to RG running and inflaton-SM couplings.

Abstract

We work out the Standard Model (SM) mass spectrum during inflation with quantum corrections, and explore its observable consequences in the squeezed limit of non-Gaussianity. Both non-Higgs and Higgs inflation models are studied in detail. We also illustrate how some inflationary loop diagrams can be computed neatly by Wick-rotating the inflation background to Euclidean signature and by dimensional regularization.

Figures (4)

• Figure 1: The 1-loop mass corrections to the gauge boson $\delta M_A^2$ as functions of the mass of the loop scalar field $m^2$. The blue, orange, and green curves correspond to the mass corrections from diagram (\ref{['vec2pt']}a) [given by Eq. (\ref{['deMADiaga']})], diagram (\ref{['vec2pt']}b) [given by Eq. (\ref{['deMB']})], and the sum of the two, respectively. The dashed line is the approximation Eq. (\ref{['deMAexpand']}).
• Figure 2: The 1-loop correction to photon's mass from a scalar with mass $m=\frac{1}{5}H$, as a function of angular quantum number $L$ of loop modes. The function $\Delta_L$ is defined as in (\ref{['dMAmodeA']}) and (\ref{['dMAmodeB']}).
• Figure 3: The quantum corrected Higgs mass $M_H$ (in unit of Hubble parameter $H$) as functions of tree level mass $M_{H0}$. The three curves from bottom to top correspond to $\lambda=(0.01, 0.1, 0.5)$, respectively.
• Figure 4: The gauge boson masses (left panel) and Yukawa couplings (right panel) as functions of Hubble scale $H$, using 2-loop SM renormalization group running. On left panel, the masses of $Z$ and $W$ (from top to bottom) are normalized by the mass of $W$; on right panel, various curves from top to bottom correspond to Yukawa couplings of $t,b,\tau,c,\mu,s,d,u,e$, respectively.