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The study of nuclei at finite temperature is of immense interest for many areas of nuclear astrophysics and nuclear-reaction science. A variety of ab initio methods are now available for computing the properties of nuclei from interactions…

Nuclear Theory · Physics 2025-04-25 Isaac G. Smith , Heiko Hergert , Scott K. Bogner

We propose a novel many-body framework combining the density matrix renormalization group (DMRG) with the valence-space (VS) formulation of the in-medium similarity renormalization group. This hybrid scheme admits for favorable…

Nuclear Theory · Physics 2023-09-12 A. Tichai , S. Knecht , A. T. Kruppa , Ö. Legeza , C. P. Moca , A. Schwenk , M. A. Werner , G. Zarand

Short-range correlations (SRCs) provide the link between low- and high-energy nuclear physics and can be quantified by two-nucleon densities. We present calculations of the two-nucleon densities using free-space similarity renormalization…

Nuclear Theory · Physics 2026-02-06 H. Y. Shang , R. Z. Hu , X. Y. Xu , Z. C. Xu , J. C. Pei , S. M. Wang

Ab initio nuclear many-body frameworks require extensive computational resources, especially when targeting heavier nuclei. Importance-truncation (IT) techniques allow to significantly reduce the dimensionality of the problem by neglecting…

Nuclear Theory · Physics 2022-03-31 J. Hoppe , A. Tichai , M. Heinz , K. Hebeler , A. Schwenk

We use the newly developed Multi-Reference In-Medium Similarity Renormalization Group to study all even isotopes of the calcium and nickel isotopic chains, based on two- plus three-nucleon interactions derived from chiral effective field…

Nuclear Theory · Physics 2014-10-29 H. Hergert , S. K. Bogner , T. D. Morris , S. Binder , A. Calci , J. Langhammer , R. Roth

We present a pedagogical introduction to the In-Medium Similarity Renormalization Group (IM-SRG) framework for ab initio calculations of nuclei. The IM-SRG performs continuous unitary transformations of the nuclear many-body Hamiltonian in…

Nuclear Theory · Physics 2016-12-28 H. Hergert

The vanguard of many-body theory is nowadays dealing with the full frequency dynamics of n-point Green's functions for n higher than two. Numerically, these objects easily become a memory bottleneck, even when working with discrete…

Strongly Correlated Electrons · Physics 2022-07-06 Sebastian Huber , Markus Wallerberger , Paul Worm , Karsten Held

The first nonperturbative version of the multireference driven similarity renormalization group (MR-DSRG) theory [C. Li and F. A. Evangelista, J. Chem. Theory Comput. $\mathbf{11}$, 2097 (2015)] is introduced. The renormalization group…

Chemical Physics · Physics 2016-05-25 Chenyang Li , Francesco A. Evangelista

Using the density matrix renormalization group method (DMRG) we calculate the magnetization of frustrated S=1/2 Heisenberg chains for various modulation patterns of the nearest neighbour coupling: commensurate, incommensurate with…

Condensed Matter · Physics 2009-10-31 F. Schönfeld , G. Bouzerar , G. S. Uhrig , E. Müller-Hartmann

Applications of the similarity renormalization group (SRG) approach [F. Wegner, Ann. Phys. 506, 77 (1994), S. D. G{\l}azek and K. G. Wilson, Phys. Rev. D 49, 4214 (1994)] to the formulation of useful many-body theories of electron…

Chemical Physics · Physics 2015-06-19 Francesco A. Evangelista

We report on recent progress of the implementation of the similarity renormalization group (SRG) for three-body interactions in a one-dimensional, bosonic model system using the plane wave basis. We discuss our implementation of the flow…

Nuclear Theory · Physics 2013-04-12 O. Åkerlund , E. J. Lindgren , J. Bergsten , B. Grevholm , P. Lerner , R. Linscott , C. Forssén , L. Platter

We introduce a hybrid approach to applying the density matrix renormalization group (DMRG) to continuous systems, combining a grid approximation along one direction with a finite Gaussian basis set along the remaining two directions. This…

Chemical Physics · Physics 2017-08-02 E. Miles Stoudenmire , Steven R. White

We present a renormalization group (RG) procedure which works naturally on a wide class of interacting one-dimension models based on perturbed (possibly strongly) continuum conformal and integrable models. This procedure integrates Kenneth…

Strongly Correlated Electrons · Physics 2016-07-05 Robert M. Konik , Yury Adamov

We employ the density matrix renormalization group (DMRG) and the wave function factorization method for the numerical solution of large scale nuclear structure problems. The DMRG exhibits an improved convergence for problems with realistic…

Nuclear Theory · Physics 2007-05-23 T. Papenbrock , D. J. Dean

We present an improved variant of the in-medium similarity renormalization group (IM-SRG) based on the Magnus expansion. In the new formulation, one solves flow equations for the anti-hermitian operator that, upon exponentiation, yields the…

Nuclear Theory · Physics 2015-10-07 T. D. Morris , N. Parzuchowski , S. K. Bogner

White's density matrix renormalization group ({DMRG}) method has been applied to the one-dimensional Ising model in a transverse field ({ITF}), in order to study the accuracy of the numerical algorithm. Due to the exact solubility of the…

Strongly Correlated Electrons · Physics 2009-10-31 Ors Legeza , Gabor Fath

We review the role played by long-distance symmetries within the context of the similarity renormalization group approach. This is based on phase-shift-preserving continuous unitary transformations that evolve Hamiltonians with a cutoff on…

Nuclear Theory · Physics 2013-02-19 E. Ruiz Arriola , V. S. Timoteo , S. Szpigel

We present a novel method, IMSRG-Net, which utilizes machine learning techniques as a solver for the in-medium Similarity Renormalization Group (IMSRG). The primary objective of IMSRG-Net is to approximate the Magnus operators $\Omega(s)$…

Nuclear Theory · Physics 2023-10-11 Sota Yoshida

We report an efficient implementation of a second-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT2) [C. Li and F. A. Evangelista, J. Chem. Theory Comput. 11, 2097 (2015)]. Our…

Chemical Physics · Physics 2016-06-22 Kevin P. Hannon , Chenyang Li , Francesco A. Evangelista

We formulate and implement the core-valence separated multireference equation-of-motion driven similarity renormalization group method (CVS-IP-EOM-DSRG) for simulating X-ray photoelectron spectra (XPS) of strongly correlated molecular…

Chemical Physics · Physics 2025-09-29 Shuhang Li , Zijun Zhao , Francesco A. Evangelista