Tensor network study of two dimensional complex \phi(4) theory at finite density

Shinichiro Akiyama, Daisuke Kadoh, Y. Kuramashi +2 more

Y. Kuramashi, 0000000563, Yoshimura Yusuke

Shinichiro Akiyama, Daisuke Kadoh, Yoshinobu Kuramashi +2 more

Abstract Tensor network is an attractive approach to the field theory with negative sign problem. The complex ϕ4 theory at finite density is a test bed for numerical algorithms to verify their effectiveness. The model shows a characteristic feature called the Silver Blaze phenomenon associated with the sign problem in the large volume limit at low temperature. We analyze the four-dimensional model employing the anisotropic tensor renormalization group algorithm with a parallel computation. We find a clear signal of the Silver Blaze phenomenon on a large volume of V = 10244, which implies that the tensor network approach is effective even for four-dimensional field theory beyond two dimensions.

Philippe Corboz

Daisuke Kadoh, Yoshinobu Kuramashi, Y. Nakamura +3 more

Abstract We study the two-dimensional complex ϕ4 theory at finite chemical potential using the tensor renormalization group. This model exhibits the Silver Blaze phenomenon in which bulk observables are independent of the chemical potential below the critical point. Since it is expected to be a direct outcome of an imaginary part of the action, an approach free from the sign problem is needed. We study this model systematically changing the chemical potential in order to check the applicability of the tensor renormalization group to the model in which scalar fields are discretized by the Gaussian quadrature. The Silver Blaze phenomenon is successfully confirmed on the extremely large volume V = 10242 and the results are also ensured by another tensor network representation with a character expansion.

Daisuke Kadoh, Y. Kuramashi, Y. Nakamura +3 more

Abstract We make a detailed analysis of the spontaneous Z 2-symmetry breaking in the two dimensional real ϕ 4 theory with the tensor renormalization group approach, which allows us to take the thermodynamic limit easily and determine the physical observables without statistical uncertainties. We determine the critical coupling in the continuum limit employing the tensor network formulation for scalar field theories proposed in our previous paper. We obtain [λ/μ c 2 ]cont. = 10.913(56) with the quartic coupling λ and the renormalized critical mass μ c . The result is compared with previous results obtained by different approaches.