F. Hiroshima and K. R. Ito 
Effective mass of nonrelativistic quantum electrodynamics
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ABSTRACT.  The effective mass $\mass$ of the nonrelativistic quantum electrodynamics with spin 1/2 is investigated. 
Let 
$\mass/m =1 + a_1(\La/m) e^2+ a_2(\La/m) e^4+ {\mathcal O}(e^6)$, 
where $m$ denotes the bare mass. $a_1(\La/m)\sim \log(\La/m)$ as $\La\rightarrow \infty$ is well known. 
Also $a_2(\La/m)\sim\sqrt{\La/m}$ is established for a spinless case. 
It is shown that 
$ {a_2(\La/m)}\sim {(\La/m)^2}$ in the case including spin $1/2$.