The quantum mechanical bound states of the −α/x2 potential are truly anomalous. We revisit this problem by adopting a slightly modified version of this potential, one that adopts a cutoff in the potential arbitrarily close to the origin. The resulting solutions are completely well-defined and “normal,” and provide us with additional insight into the solutions of the “bare” −α/x2 potential. We present results here as a case study in undergraduate research—two independent methodologies are used: one analytical (albeit with very unfamiliar non-elementary functions) and one numerical (with a very straightforward methodology). These play complementary roles in arriving at solutions and achieving insights into this problem.
REFERENCES
1.
K. M.
Case
, “
Singular potentials
,” Phys. Rev.
80
, 797
–806
(1950
).2.
P. M.
Morse
and
H.
Feshbach
, Methods of Theoretical Physics, Part II
(
McGraw-Hill Book Company, Inc
.,
Toronto
, 1953
), pp. 1665
–1667
.3.
L. D.
Landau
and
E. M.
Lifshitz
, Quantum Mechanics: Non-Relativistic Theory
(
Pergamon Press
,
Toronto
, 1977
). See Sec. 35, but also Sec. 18 for more general remarks concerning singular potentials, of which the subject of this paper is one.4.
S. A.
Coon
and
B. R.
Holstein
, “
Anomalies in quantum mechanics: The
potential
,” Am. J. Phys.
70
, 513
–519
(2002
).5.
A. M.
Essin
and
D. J.
Griffiths
, “
Quantum mechanics of the
potential
,” Am. J. Phys.
74
, 109
–117
(2006
).6.
D. J.
Griffiths
and
D. F.
Schroeter
, Introduction to Quantum Mechanics
, 3rd ed. (
Cambridge U. P
.,
Cambridge
, 2018
), pp. 86
–87
. This exposition takes the form of a problem, and provides an introduction to the treatment provided in Ref. 5.7.
J.-M.
Lévy-Leblond
, “
Electron capture by polar molecules
,” Phys. Rev.
153
, 1
–4
(1967
).8.
F.
Marsiglio
, “
The harmonic oscillator in quantum mechanics: A third way
,” Am. J. Phys.
77
, 253
–258
(2009
).9.
V.
Jelic
and
F.
Marsiglio
, “
The double-well potential in quantum mechanics: A simple, numerically exact formulation
,” Eur. J. Phys.
33
, 1651
–1666
(2012
).10.
K.
Randles
and
D. V.
Schroeder
, “
Quantum matrix diagonalization visualized
,” Am. J. Phys.
87
, 857
–861
(2019
).11.
B. A.
Jugdutt
and
F.
Marsiglio
, “
Solving for three-dimensional central potentials using numerical matrix methods
,” Am. J. Phys.
81
, 343
–350
(2013
).12.
G.
Arfken
, Mathematical Methods for Physicists
(
Academic Press
,
Toronto
, 1985
), pp. 573
–636
.13.
M.
Abramowitz
and
I. A.
Stegun
, Handbook of Mathematical Functions
(
Dover
,
New York
, 1964
), pp. 231
–232
.14.
F. W.
Olver
,
D. W.
Lozier
,
R. F.
Boisvert
, and
C. W.
Clark
, NIST Handbook of Mathematical Functions
(
Cambridge U. P.
, Cambridge
, 2010
), pp. 248
–261
.15.
A.
Gil
,
J.
Segura
, and
N. M.
Temme
, “
Computing solutions of the modified Bessel differential equation for imaginary orders and positive arguments
,” ACM Trans. Math. Software
30
, 145
–158
(2004
).© 2020 American Association of Physics Teachers.
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