The critical behavior of d-dimensional systems with an n-component order parameter is reconsidered at (m,d,n)-Lifshitz points, where a wave-vector instability occurs in an m-dimensional subspace of ${ \mathbb R}^d$. Our aim is to sort out which ones of the previously published partly contradictory $\epsilon$-expansion results to second order in $\epsilon=4+\frac{ m}{ 2}-d$ are correct. To this end, a field-theory calculation is performed directly in the position space of $d=4+\frac{ m}{ 2}-\epsilon$ dimensions, using dimensional regularization and minimal subtraction of ultraviolet poles. The residua of the dimensionally regularized integrals that are required to determine the series expansions of the correlation exponents $\eta_{ l2}$ and $\eta_{ l4}$ and of the wave-vector exponent $\beta_q$ to order $\epsilon^2$ are reduced to single integrals, which for general m=1,...,d-1 can be computed numerically, and for special values of m, analytically. Our results are at variance with the original predictions for general m. For m=2 and m=6, we confirm the results of Sak and Grest [Phys. Rev. B { \bf 17}, 3602 (1978)] and Mergulh{ \~a}o and Carneiro's recent field-theory analysis [Phys. Rev. B { \bf 59},13954 (1999)].
Categories: cond-mat.stat-mech hep-th