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Over the past decade the in-medium similarity renormalization group (IMSRG) approach has proven to be a powerful and versatile ab initio many-body method for studying medium-mass nuclei. So far, the IMSRG was limited to the approximation in…

Nuclear Theory · Physics 2021-04-27 M. Heinz , A. Tichai , J. Hoppe , K. Hebeler , A. Schwenk

We describe an approximation to the in-medium similarity renormalization group (IMSRG) method in which we include the effects of intermediate three-body operators arising within nested commutators. As an initial step, we present the…

Nuclear Theory · Physics 2025-01-09 B. C. He , S. R. Stroberg

We present a pedagogical discussion of Similarity Renormalization Group (SRG) methods, in particular the In-Medium SRG (IMSRG) approach for solving the nuclear many-body problem. These methods use continuous unitary transformations to…

Nuclear Theory · Physics 2017-06-28 H. Hergert , S. K. Bogner , J. G. Lietz , T. D. Morris , S. J. Novario , N. M. Parzuchowski , F. Yuan

The in-medium similarity renormalization group (IMSRG) is a popular many-body method used for computations of nuclei. It solves the many-body Schr\"odinger equation through a continuous unitary transformation of the many-body Hamiltonian.…

Nuclear Theory · Physics 2026-04-28 Matthias Heinz

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 use the recently proposed In-Medium Similarity Renormalization Group (IM-SRG) to carry out a systematic study of closed-shell nuclei up to $\nuc{Ni}{56}$, based on chiral two- plus three-nucleon interactions. We analyze the capabilities…

Nuclear Theory · Physics 2013-04-02 H. Hergert , S. K. Bogner , S. Binder , A. Calci , J. Langhammer , R. Roth , A. Schwenk

We benchmark two implementations of the in-medium similarity renormalization group (IMSRG) method, IMSRG(2) and IMSRG(2*), for the low-lying states of a pairing-plus-particle-hole model with varying numbers of fermions. In IMSRG(2), all…

Nuclear Theory · Physics 2025-08-13 L. H. Chen , Y. G. Yao , B. C. He

We present a comprehensive review of the In-Medium Similarity Renormalization Group (IM-SRG), a novel ab inito method for nuclei. The IM-SRG employs a continuous unitary transformation of the many-body Hamiltonian to decouple the ground…

Nuclear Theory · Physics 2016-03-15 H. Hergert , S. K. Bogner , T. D. Morris , A. Schwenk , K. Tsukiyama

The in-medium similarity renormalization group (IMSRG) is a powerful and flexible many-body method to compute the structure of nuclei starting from nuclear forces. Recent developments have extended the IMSRG from its standard truncation at…

Nuclear Theory · Physics 2025-03-12 M. Heinz , T. Miyagi , S. R. Stroberg , A. Tichai , K. Hebeler , A. Schwenk

We formulate the In-Medium Similarity Renormalization Group (IM-SRG) for open-shell nuclei using a multi-reference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multi-reference IM-SRG…

Nuclear Theory · Physics 2013-06-13 H. Hergert , S. Binder , A. Calci , J. Langhammer , R. Roth

Efforts to describe nuclear structure and dynamics from first principles have advanced significantly in recent years. Exact methods for light nuclei are now able to include continuum degrees of freedom and treat structure and reactions on…

The non-perturbative {\it ab initio} calculations of infinite nuclear matter using In-Medium Similarity Renormalization Group (IMSRG) method is developed in this work, which enables calculations with chiral two and three-nucleon forces at…

Nuclear Theory · Physics 2025-02-27 Xin Zhen , Rongzhe Hu , Haoyu Shang , Jiawei Chen , Junchen Pei , Furong Xu

We present a new ab-initio method that uses similarity renormalization group (SRG) techniques to continuously diagonalize nuclear many-body Hamiltonians. In contrast with applications of the SRG to two- and three-nucleon interactions in…

Nuclear Theory · Physics 2011-07-21 K. Tsukiyama , S. K. Bogner , A. Schwenk

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

Functional renormalization group (FRG) is applied to the three-body scattering problem in the two-component fermionic system with an attractive contact interaction. We establish a new and correct flow equation on the basis of FRG and show…

Quantum Gases · Physics 2013-11-05 Yuya Tanizaki

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

This work introduces various approaches to include connected three-body terms in unitary many-body theories, focusing a representative example on the driven similarity renormalization group (DSRG). Starting from the least approximate method…

Chemical Physics · Physics 2020-07-15 Chenyang Li , Francesco A. Evangelista

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 present a status report on the ongoing analysis of the 3D Ising model with nearest-neighbor interactions using the Monte Carlo Renormalization Group (MCRG) and finite size scaling (FSS) methods on $64^3$, $128^3$, and $256^3$ simple…

Condensed Matter · Physics 2015-06-25 Rajan Gupta , Pablo Tamayo

We investigate the Ising and Heisenberg models using the Block Renormalization Group Method (BRGM), focusing on its behavior across different system sizes. The BRGM reduces the number of spins by a factor of 1/2 (1/3) for the Ising…

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