filmstrip of the SRG

Similarity Renormalization Group for Nuclear Physics

Welcome to the SRG home page!

This website is maintained by Dick Furnstahl ( and his collaborators (including Eric Anderson, Scott Bogner, Eric Jurgenson, Robert Perry, Lucas Platter, Achim Schwenk, and Kyle Wendt). It will be updated at irregular intervals with new pictures, movies, and links. You are invited to send email with suggestions for new content or questions on what you see.

The research results presented here were supported in part by the National Science Foundation under Grant Nos. PHY-0354916 and PHY-0653312 and by the UNEDF SciDAC Collaboration under DOE grant DE-FC02-07ER41457.

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Overview and References


The similarity renormalization group (SRG) for low-energy nuclear physics is based on unitary transformations that suppress off-diagonal matrix elements, forcing the hamiltonian towards a band-diagonal form. A simple SRG transformation applied to nucleon-nucleon interactions leads to greatly improved convergence properties while preserving observables, and provides a method to consistently evolve many-body potentials and other operators.

General references on the SRG and related Hamiltonian Flow Equations

  1. The Flow Equation Approach to Many-Particle Systems, Stefan Kehrein (Springer, Berlin, 2006).
  2. Renormalization of Hamiltonians, S.D. Glazek and K.G. Wilson, Phys. Rev. D 48, 5863 (1993).
  3. Flow Equations for Hamiltonians, F. Wegner, Annalen der Physik (Leipzig) 3, 77 (1994).
  4. Flow Equations for Hamiltonians, F. Wegner, Physics Reports 348, 77 (2001).
  5. Perturbative renormalization group for Hamiltonians, S.D. Glazek and K.G. Wilson, Phys. Rev. D 49, 4214 (1994).
  6. Asymptotic freedom and bound states in Hamiltonian dynamics, S.D. Glazek and K.G. Wilson, Phys. Rev. D 57, 3558 (1998), [hep-th/9707028].
  7. Limit cycles in quantum theories, S.D. Glazek and K.G. Wilson, Phys. Rev. Lett. 89, 230401 (2002), [hep-th/0203088].
  8. Flow Equations and Normal Ordering, E. Koerding and F. Wegner, cond-mat/0509801.
  9. Flow Equations and Normal Ordering. A Survey, F. Wegner, cond-mat/0511660.
  10. Limit cycles of effective theories, S.D. Glazek, Phys. Rev. D 75, 025005 (2007), [hep-th/0611015].

References on the SRG for Nuclear Physics:

  1. From low-momentum interactions to nuclear structure, S.K. Bogner, R.J. Furnstahl, and A. Schwenk, to be published in Progress in Particle and Nuclear Physics. This is an overview of low-momentum interactions for nuclear physics, including the SRG results.
  2. Similarity renormalization group for nucleon-nucleon interactions, S.K. Bogner, R.J. Furnstahl, and R.J. Perry, Phys. Rev. C 75, 061001(R) (2007), [nucl-th/0611045]. This is probably the best place to start for learning about how the SRG can be applied to low-energy nuclear physics.
  3. Are low-energy nuclear observables sensitive to high-energy phase shifts?, S.K. Bogner, R.J. Furnstahl, R.J. Perry, and A. Schwenk, Phys. Lett. B 649, 488 (2007), [nucl-th/0701013]. This paper shows how the SRG decouples low-energy from high-energy physics.
  4. The Unitary Correlation Operator Method from a similarity renormalization group perspective, H. Hergert and R. Roth, Phys. Rev. C. 75, 051001(R) (2007), [nucl-th/0703006]. The UCOM method of unitary transformations is related to the SRG.
  5. Three-body forces produced by a similarity renormalization group transformation in a simple model, S.K. Bogner, R.J. Furnstahl, and R.J. Perry, Ann. Phys. (NY) 323, 1478 (2008), [arXiv:0708.1602]. This is a pedagogical paper that shows in detail using a very simple model (only 2x2 matrices!) how the SRG works for two- and three-body interactions. A diagrammatic approach to the SRG equations is introduced and applied.
  6. Convergence in the no-core shell model with low-momentum two-nucleon interactions, S.K. Bogner, R.J. Furnstahl, P. Maris, R.J. Perry, A. Schwenk, and J.P. Vary, Nucl. Phys. A801, 21 (2008) [arXiv:0708.3754]. Application of the SRG with only NN interactions (no three-body) to few-body systems up to Li-7 to show the improved convergence with SRG running.
  7. Decoupling in the similarity renormalization group for nucleon-nucleon forces, E.D. Jurgenson, S.K. Bogner, R.J. Furnstahl, and R.J. Perry, Phys. Rev. C 78, 014003 (2008) [arXiv:0711.4252]. This paper explores in detail how decoupling plays out in the SRG.
  8. Block diagonalization using srg flow equations, E. Anderson, S.K. Bogner, R.J. Furnstahl, E.D. Jurgenson, R.J. Perry, and A. Schwenk, Phys. Rev. C 77, 037001 (2008) [arXiv:0801.1098]. This paper shows how one can choose different generators for the SRG to get different patterns of decoupling in a Hamiltonian. In particular, block diagonalization.
  9. The impact of bound states on similarity renormalization group transformations, S.D. Glazek and R.J. Perry, Phys. Rev. D 78, 045011 (2008) [arXiv:0803.2911]. This paper examines the convergence properties of SRG transformations with Wegner's transformation and a simpler transformation used in most of the nuclear physics applications to date.
  10. Similarity Renormalization Group Evolution of Many-Body Forces in a One-Dimensional Model, E.D. Jurgenson and R.J. Furnstahl [arXiv:0809.4199]. Many-body forces are evolved in a translationally invariant harmonic oscillator basis using a one-dimensional model as a test case.
  11. Nuclear matter from chiral low-momentum interactions, S.K. Bogner, R.J. Furnstahl, A. Nogga, and A. Schwenk. Nuclear matter calculation based on low-momentum interactions, including SRG interactions.
  12. Evolution of Nuclear Many-Body Forces with the Similarity Renormalization Group, E.D. Jurgenson, P. Navratil, R.J. Furnstahl, Phys. Rev. Lett. 103, 082501 (2009) [arXiv:0905.1873]. Evolution of 3N forces in a harmonic oscillator basis.
  13. Applications of the Similarity Renormalization Group to the Nuclear Interaction, E.D. Jurgenson. This is Eric Jurgenson's thesis. Lots of good info here!

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Talks on the SRG for Nuclear Physics

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Unpublished Explorations of the SRG

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Movies of the SRG and Vlow k in Action

The Similarity Renormalization Group (SRG) and Vlow k potentials evolve as a parameter is lowered. For the SRG, it is lambda, which is a measure of the spread of the momentum-space potential about the diagonal. For Vlow k, it is the momentum cutoff Lambda. There is a rough correspondence between the potentials at numerically similar values of lambda and Lambda. The units of the potentials are fm (hbar2/M = 1).

The movies here depict the evolution of the potentials (and related quantities) with lambda and Lambda.

SRG Evolved Vsrg

SRG Evolved Operators (other than the hamiltonian)

Cutoff Evolved Vlow k

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Included here are both color contour plots and ordinary figures.

SRG Evolved Vsrg

Deuteron Properties for Vsrg and Vlow k

Shown are the binding energy and asymptotic D/S ratio, which are observables, and the D-state probability, which is not, as a function of lambda or Lambda.

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Links to other SRG-Related Sites

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Your comments and suggestions are appreciated.
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SRG for Nuclear Physics.
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