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TZID:America/Chicago
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DTSTART:20221106T020000
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DTSTART:20220313T020000
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BEGIN:VEVENT
UID:calendar.20635.field_event_date_2.0@physics.wustl.edu
CREATED:20220912T131300Z
DESCRIPTION:A paramount goal in the field of nuclear physics is to unify ab
-initio treatments of bound and unbound states. The position-space quantum
Monte Carlo (QMC) methods have a long history of successful bound state c
alculations in light systems but so far have seen very little application
to unbound systems. Here we introduce a numerical method to improve the ef
ficiency and accuracy of unbound-state calculations in QMC, and as an ini
tial application we compute scattering observables for the neutron-triton
system using variational Monte Carlo (VMC) wave functions. The method cons
ists of inferring long-range amplitudes in the wave function from integral
s over the short-ranged region where all the particles interact. This appr
oach using integral relations is well established in the literature; here
we develop it for the QMC framework. We validate our code with a consiste
ncy check between short-range spectroscopic overlap functions computed fro
m direct evaluation and from the integral relations; scattering amplitude
s are long-range asymptotics of those overlaps. Comparison against publish
ed benchmark calculations using the same potential demonstrates that the i
ntegral method, when applied to the current VMC wave functions, produces
more accurate scattering observables than direct evaluation from the same
variational wave function. However, it still differs noticeably from exa
ct results. We then present phase shifts and mixing parameters for the n +
3H system using additional interactions. In particular, we present one o
f the first applications of the Norfolk family of local coordinate-space c
hiral potentials in unbound systems of A > 2. The Norfolk results accurate
ly describe s-wave scattering but predict p-wave cross sections that are t
oo large. Compared with previous QMC scattering calculations, the integra
l method avoids difficulties associated with precise computation of energy
differences and with convergence outside the interaction region, which a
re particularly severe in the variational calculation.
DTSTART;TZID=America/Chicago:20220923T120000
DTEND;TZID=America/Chicago:20220923T120000
LAST-MODIFIED:20220923T183006Z
LOCATION:38.649462, -90.305046
SUMMARY:Nuclear Physics Seminar with Abraham Flores on Variational Monte Ca
rlo Calculations
URL;TYPE=URI:https://physics.wustl.edu/events/nuclear-physics-seminar-abrah
am-flores-variational-monte-carlo-calculations
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