| 1. |
- Acharya, B., et al.
(författare)
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Effective-field-theory predictions of the muon-deuteron capture rate
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- We quantify the theoretical uncertainties of chiral effective-field-theory predictions of the muon-deuteron capture rate. Theoretical error estimates of this low-energy process are important for a reliable interpretation of forthcoming experimental results by the MuSun Collaboration. Specifically, we estimate the three dominant sources of uncertainties that impact theoretical calculations of this rate: those resulting from uncertainties in the pool of fit data used to constrain the coupling constants in the nuclear interaction, those due to the truncation of the effective field theory, and those due to uncertainties in the axial radius of the nucleon. For the capture rate into the S01 channel, we find an uncertainty of approximately 4.6s-1 due to the truncation in the effective field theory and an uncertainty of 3.9s-1 due to the uncertainty in the axial radius of the nucleon, both of which are similar in size to the targeted experimental precision of a few percent.
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| 2. |
- Bedaque, P., et al.
(författare)
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Quark mass variation constraints from Big Bang nucleosynthesis
- 2011
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 83:4
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Tidskriftsartikel (refereegranskat)abstract
- We study the impact on the primordial abundances of light elements created by a variation of the quark masses at the time of Big Bang nucleosynthesis (BBN). In order to navigate through the particle and nuclear physics required to connect quark masses to binding energies and reaction rates in a model-independent way, we use lattice QCD data and a hierarchy of effective field theories. We find that the measured 4He abundances put a bound of -1%≲δmq/mq≲0.7% on a possible variation of quark masses. The effect of quark mass variations on the deuterium abundances can be largely compensated by changes of the baryon-to-photon ratio η. Including bounds on the variation of η coming from WMAP results and adding some additional assumptions further narrows the range of allowed values of δmq/mq.
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| 3. |
- Bogner, S. K., et al.
(författare)
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Density matrix expansion for low-momentum interactions
- 2009
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Ingår i: European Physical Journal A. - 1434-601X .- 1434-6001. ; 39:2, s. 219-241
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Tidskriftsartikel (refereegranskat)abstract
- A first step toward a universal nuclear energy density functional based on low-momentum interactions is taken using the density matrix expansion (DME) of Negele and Vautherin. The DME is adapted for non-local momentum space potentials and generalized to include local three-body interactions. Different prescriptions for the three-body DME are compared. Exploratory results are given at the Hartree-Fock level, along with a roadmap for systematic improvements within an effective action framework for the Kohn-Sham density functional theory.
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| 4. |
- Braaten, E., et al.
(författare)
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Efimov physics in Li-6 atoms
- 2010
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 81:1
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Tidskriftsartikel (refereegranskat)abstract
- A new narrow three-atom loss resonance associated with an Efimov trimer crossing the three-atom threshold has recently been discovered in a many-body system of ultracold Li-6 atoms in the three lowest hyperfine spin states at a magnetic field near 895 G. O'Hara and coworkers have used measurements of the three-body recombination rate in this region to determine the complex three-body parameter associated with Efimov physics. Using this parameter as the input, we calculate the universal predictions for the spectrum of Efimov states and for the three-body recombination rate in the universal region above 600 G where all three scattering lengths are large. We predict an atom-dimer loss resonance at 672 +/- 2G associated with an Efimov trimer disappearing through an atom-dimer threshold. We also predict an interference minimum in the three-body recombination rate at 759 +/- 1G where the three-spin mixture may be sufficiently stable to allow experimental study of the many-body system.
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| 5. |
- Braaten, E., et al.
(författare)
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Exact relations for a strongly interacting fermi gas from the operator product expansion
- 2008
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 100:20
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Tidskriftsartikel (refereegranskat)abstract
- The momentum distribution in a Fermi gas with two spin states and a large scattering length has a tail that falls off like 1/k(4) at large momentum k, as pointed out by Tan. He used novel methods to derive exact relations between the coefficient of the tail in the momentum distribution and various other properties of the system. We present simple derivations of these relations using the operator product expansion for quantum fields. We identify the coefficient as the integral over space of the expectation value of a local operator that measures the density of pairs.
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| 6. |
- Braaten, E., et al.
(författare)
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Renormalization in the three-body problem with resonant p-wave interactions
- 2012
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Resonant p-wave interactions can be described by a minimal zero-range model defined by a truncated effective range expansion so that the only two-body interaction parameters are the inverse scattering volume 1/a(p) and the p-wave effective range r(p). This minimal model can be formulated as a local quantum field theory with a p-wave interaction between atom fields and a molecular field. In the two-atom sector, the model is renormalizable, but it has unphysical behavior at high energies because there are negative-probability states with momentum scale r(p). In the sector with three atoms, two of which are identical, renormalization in some parity and angular momentum channels involves an ultraviolet limit cycle, indicating asymptotic discrete scale invariance. The Efimov effect occurs in the unitary limit a(p)(-1/3),r(p) -> 0, but this limit is unphysical because there are low-energy states with negative probability. The minimal model can be of physical relevance only at energies small compared to the energy scale set by r(p) where the effects of negative-probability states are suppressed.
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| 7. |
- Braaten, E., et al.
(författare)
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Short-Time Operator Product Expansion for rf Spectroscopy of a Strongly Interacting Fermi Gas
- 2010
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 104:22
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Tidskriftsartikel (refereegranskat)abstract
- Universal relations that hold for any state provide powerful constraints on systems consisting of fermions with two spin states interacting with a large scattering length. In radio-frequency (rf) spectroscopy, the mean shift in the rf frequency and the large-frequency tail of the rf transition rate are proportional to the contact, which measures the density of pairs with small separations. We show that these universal relations can be derived and extended by using the short-time operator product expansion of quantum field theory. This is a general method for identifying aspects of many-body physics that are controlled by few-body physics.
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| 8. |
- Braaten, Eric, et al.
(författare)
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Universal Relations for Identical Bosons from Three-Body Physics
- 2011
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 106:15, s. 153005-
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Tidskriftsartikel (refereegranskat)abstract
- Systems consisting of identical bosons with a large scattering length satisfy universal relations determined by 2-body physics that are similar to those for fermions with two spin states. They require the momentum distribution to have a large-momentum 1/k4 tail and the radio-frequency transition rate to have a high-frequency 1/ω3/2 tail, both of which are proportional to the 2-body contact. Identical bosons also satisfy additional universal relations that are determined by 3-body physics and involve the 3-body contact, which measures the probability of 3 particles being very close together. The coefficients of the 3-body contact in the 1/k5 tail of the momentum distribution and in the 1/ω2 tail of the radio-frequency transition rate are log-periodic functions of k and ω that depend on the Efimov parameter.
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| 9. |
- Deltuva, A., et al.
(författare)
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Universality in Four-Body Scattering
- 2011
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 51:2-4, s. 235-247
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Tidskriftsartikel (refereegranskat)abstract
- The four-body system is studied in the limit of large two-body scattering length by solving momentum-space integral equations for the transition operators or, alternatively, configuration-space equations for wave function. A number of universal results for atom-trimer and dimer-dimer scattering observables are found. We furthermore address the question whether the universal four-body systems contain additional states besides the known two S-wave states.
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| 10. |
- Drut, J. E., et al.
(författare)
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Exact-exchange density functional theory for neutron drops
- 2011
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 84:1
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Tidskriftsartikel (refereegranskat)abstract
- We compute the ground-state properties of finite systems of neutrons in an external harmonic trap, interacting via the Minnesota potential, using the "exact-exchange" form of orbital-dependent density functional theory. We compare our results with Hartree-Fock calculations and find very close agreement. Within the context of the interaction studied, we conclude that this simple orbital-dependent functional brings conventional nuclear density functional theory to the level of Hartree-Fock in an ab initio fashion. Our work is a first step toward higher order ab initio nuclear functionals based on realistic nucleon-nucleon interactions.
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