Physics Faculty Publications
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https://digitalcommons.bowdoin.edu/physicsfacultypublications
Recent documents in Physics Faculty Publications
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Thu, 01 Jun 2023 14:41:16 PDT
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Quantum lifetime of twodimensional holes
https://digitalcommons.bowdoin.edu/physicsfacultypublications/164
https://digitalcommons.bowdoin.edu/physicsfacultypublications/164
Thu, 11 May 2023 12:58:43 PDT
The quantum lifetime of twodimensional holes in a GaAs/AlGaAs double quantum well is determined via tunneling spectroscopy. At low temperatures the lifetime is limited by impurity scattering but at higher temperatures holehole Coulomb scattering dominates. Our results are consistent with the Fermi liquid theory, at least up to rs = 11. At the highest temperatures the measured width of the hole spectral function becomes comparable to the Fermi energy. A new, tunnelingspectroscopic method for determining the inplane effective mass of the holes is also demonstrated. © 2007 Elsevier Ltd. All rights reserved.
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J. P. Eisenstein et al.

Construction and validation of UVC decontamination cabinets for filtering facepiece respirators: Comment
https://digitalcommons.bowdoin.edu/physicsfacultypublications/163
https://digitalcommons.bowdoin.edu/physicsfacultypublications/163
Thu, 11 May 2023 12:58:42 PDT
In their September 2020 paper [Appl. Opt.59, 7585 (2020)], Purschke et al . report UVC transmittance measurements of N95 filtering facepiece respirators (FFRs), including the 3M 1860, which is one of the most widely used FFRs.We have also measured the transmittance of this FFRin our two separate laboratories with multiple FFR samples, and we have obtained transmittance values similar to one another, but very different from what Purschke et al . reported for two of the four FFR layers.
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Anant Agrawal et al.

Quantum kinks: Solitons at strong coupling
https://digitalcommons.bowdoin.edu/physicsfacultypublications/162
https://digitalcommons.bowdoin.edu/physicsfacultypublications/162
Thu, 11 May 2023 12:58:42 PDT
We examine solitons in theories with heavy fermions. These "quantum" solitons differ dramatically from semiclassical (perturbative) solitons because fermion loop effects are important when the Yukawa coupling is strong. We focus on kinks in a (1 + 1)dimensional 4 theory coupled to fermions; a largeN expansion is employed to treat the Yukawa coupling g nonperturbatively. A local expression for the fermion vacuum energy is derived using the WKB approximation for the Dirac eigenvalues. We find that fermion loop corrections increase the energy of the kink and (for large g) decrease its size. For large g, the energy of the quantum kink is proportional to g, and its size scales as 1g, unlike the classical kink; we argue that these features are generic to quantum solitons in theories with strong Yukawa couplings. We also discuss the possible instability of fermions to solitons. © 1992 The American Physical Society.
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Stephen G. Naculich

Can the electroweak symmetrybreaking sector be hidden?
https://digitalcommons.bowdoin.edu/physicsfacultypublications/161
https://digitalcommons.bowdoin.edu/physicsfacultypublications/161
Thu, 11 May 2023 12:58:41 PDT
In a recent paper, Chivukula and Golden claimed that the electroweak symmetrybreaking sector could be hidden if there were many inelastic channels in the longitudinal WW scattering process. They presented a model in which the W's couple to pseudoGoldstone bosons, which may be difficult to detect experimentally. Because of these inelastic channels, thw WW interactions do not become strong in the TeV region. We demonstrate that, despite the reduced WW elastic amplitudes in this model, the total event rate (∼ 5000 extra longitudinal W+W pairs produced in one standard SSC year) does not decrease with an increasing number of inelastic channels, and is roughly the same as in a model with a broad highenergy resonance and no inelastic channels. © 1992.
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S. G. Naculich et al.

Thirdgeneration effects on fermion mass predictions in supersymmetric grand unified theories
https://digitalcommons.bowdoin.edu/physicsfacultypublications/159
https://digitalcommons.bowdoin.edu/physicsfacultypublications/159
Thu, 11 May 2023 12:58:40 PDT
Relations among fermion masses and mixing angles at the scale of grand unification are modified at lower energies by renormalization group running induced by gauge and Yukawa couplings. In supersymmetric theories, the b quark and lepton Yukawa couplings, as well as the t quark coupling, may cause significant running if tan, the ratio of Higgs field expectation values, is large. We present approximate analytic expressions for the scaling factors for fermion masses and CKM matrix elements induced by all three third generation Yukawa couplings. We then determine how running caused by the third generation of fermions affects the predictions arising from three possible forms for the Yukawa coupling matrices at the GUT scale: the GeorgiJarlskog, Giudice, and Fritzsch textures. © 1993 The American Physical Society.
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Stephen G. Naculich

Inelastic channels in the electroweak symmetrybreaking sector
https://digitalcommons.bowdoin.edu/physicsfacultypublications/160
https://digitalcommons.bowdoin.edu/physicsfacultypublications/160
Thu, 11 May 2023 12:58:40 PDT
It has been argued that if light Higgs bosons do not exist then the selfinteractions of W's become strong in the TeV region and can be observed in longitudinal WW scattering. We present a model with many inelastic channels in the WW scattering process, corresponding to the creation of heavy fermion pairs. The presence of these heavy fermions affects the elastic scattering of W's by propagating in loops, greatly reducing the amplitudes in some charge channels. Consequently, the symmetrybreaking sector cannot be fully explored by using, for example, the W+W+ mode alone; all WW→WW scattering modes must be measured. © 1992.
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S. G. Naculich et al.

Inelastic channels in WW scattering
https://digitalcommons.bowdoin.edu/physicsfacultypublications/158
https://digitalcommons.bowdoin.edu/physicsfacultypublications/158
Thu, 11 May 2023 12:58:39 PDT
If the electroweak symmetrybreaking sector becomes strongly interacting at high energies, it can be probed through longitudinal W scattering. We present a model with many inelastic channels in the WLWL scattering process, corresponding to the production of heavy fermion pairs. These heavy fermions affect the elastic scattering of WL's by propagating in loops, greatly reducing the amplitudes in some charge channels. We conclude that the symmetrybreaking sector cannot be fully explored by using, for example, the WL±WL± mode alone, even when no resonance is present; all WLWL→WLWL scattering modes must be measured. © 1993 The American Physical Society.
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S. G. Naculich et al.

String calculation of QCD Wilson loops on arbitrary surfaces
https://digitalcommons.bowdoin.edu/physicsfacultypublications/156
https://digitalcommons.bowdoin.edu/physicsfacultypublications/156
Thu, 11 May 2023 12:58:38 PDT
Compact string expressions are found for nonintersecting Wilson loops in SU(N) YangMills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included. © 1995 The American Physical Society.
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Stephen G. Naculich et al.

Simplecurrent symmetries, ranklevel duality, and linear skein relations for ChernSimons graphs
https://digitalcommons.bowdoin.edu/physicsfacultypublications/157
https://digitalcommons.bowdoin.edu/physicsfacultypublications/157
Thu, 11 May 2023 12:58:38 PDT
A previously proposed twostep algorithm for calculating the expectation values of arbitrary ChernSimons graphs fails to determine certain crucial signs. The step which involves calculating tetrahedra by solving certain nonlinear equations is repaired by introducing additional linear equations. The step which involves reducing arbitrary graphs to sums of products of tetrahedra remains seriously disabled, apart from a few exceptional cases. As a first step towards a new algorithm for general graphs we find useful linear equations for those special graphs which support knots and links. Using the improved set of equations for tetrahedra we examine the symmetries between tetrahedra generated by arbitrary simple currents. Along the way we describe the simple, classical origin of simplecurrent charges. The improved skein relations also lead to exact identities between planar tetrahedra in level K G(N) and level N G(K) ChernSimons theories, where G(N) denotes a classical group. These results are recast as WZW braidmatrix identities and as identities between quantum 6jsymbols at appropriate roots of unity. We also obtain the transformation properties of arbitrary graphs, knots, and links under simplecurrent symmetries and ranklevel duality. For links with knotted components this requires precise control of the braid eigenvalue permutation signs, which we obtain from plethysm and an explicit expression for the (multiplicityfree) signs, valid for all compact gauge groups and all fusion products. © 1993.
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Stephen G. Naculich et al.

Fermions destabilize electroweak strings
https://digitalcommons.bowdoin.edu/physicsfacultypublications/155
https://digitalcommons.bowdoin.edu/physicsfacultypublications/155
Thu, 11 May 2023 12:58:37 PDT
Z strings in the WeinbergSalam model including fermions are unstable for all values of the parameters. The cause of this instability is the fermion vacuum energy in the Zstring background. Z strings with nonzero fermion densities, however, may still be stable. © 1995 The American Physical Society.
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Stephen G. Naculich

Large N universality of the twodimensional YangMills string
https://digitalcommons.bowdoin.edu/physicsfacultypublications/154
https://digitalcommons.bowdoin.edu/physicsfacultypublications/154
Thu, 11 May 2023 12:58:36 PDT
We exhibit the gaugegroup independence ("universality") of all normalized nonintersecting Wilson loop expectation values in the large N limit of twodimensional YangMills theory. This universality is most easily understood via the string theory reformulation of these gauge theories. By constructing an isomorphism between the string maps contributing to normalized Wilson loop expectation values in the different theories, we prove the large N universality of these observables on any surface. The string calculation of the Wilson loop expectation value on the sphere also leads to an indication of the large N phase transition separating strong and weakcoupling phases. © 1995.
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Michael Crescimanno et al.

Evaluation of the free energy of twodimensional YangMills theory
https://digitalcommons.bowdoin.edu/physicsfacultypublications/153
https://digitalcommons.bowdoin.edu/physicsfacultypublications/153
Thu, 11 May 2023 12:58:35 PDT
The free energy in the weakcoupling phase of twodimensional YangMills theory on a sphere for [Formula presented] and [Formula presented] is evaluated in the [Formula presented] expansion using the techniques of Gross and Matytsin. Many features of YangMills theory are universal among different gauge groups in the large [Formula presented] limit, but significant differences arise in subleading order in [Formula presented]. © 1996 The American Physical Society.
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Michael Crescimanno et al.

Superconformal coset equivalence from levelrank duality
https://digitalcommons.bowdoin.edu/physicsfacultypublications/152
https://digitalcommons.bowdoin.edu/physicsfacultypublications/152
Thu, 11 May 2023 12:58:34 PDT
We construct a onetoone map between the primary fields of the N = 2 superconformal KazamaSuzuki models G(m, n, k) and G(k, n, m) based on complex Grassmannian cosets, using levelrank duality of WessZuminoWitten models. We then show that conformal weights, superconformal U(1) charges, modular transformation matrices, and fusion rules are preserved under this map, providing strong evidence for the equivalence of these coset models. © 1997 Elsevier Science B.V.
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Stephen G. Naculich et al.

Oneinstanton test of a SeibergWitten curve from Mtheory: The antisymmetric representation of SU(N)
https://digitalcommons.bowdoin.edu/physicsfacultypublications/151
https://digitalcommons.bowdoin.edu/physicsfacultypublications/151
Thu, 11 May 2023 12:58:33 PDT
Oneinstanton predictions are obtained from the SeibergWitten curve derived from Mtheory by Landsteiner and Lopez for the Coulomb branch of N = 2 supersymmetric SU(N) gauge theory with a matter hypermultiplet in the antisymmetric representation. Since this cubic curve describes a Riemann surface that is nonhyperelliptic, a systematic perturbation expansion about a hyperelliptic curve is developed, with a comparable expansion for the SeibergWitten differential. Calculation of the period integrals of the SW differential by the method of residues of D'Hoker, Krichever, and Phong enables us to compute the prepotential explicitly to oneinstanton order. It is shown that the oneinstanton predictions for SU(2), SU(3), and SU(4) agree with previously available results. For SU(N), N ≥ 5, our analysis provides explicit predictions of a curve derived from Mtheory at the oneinstanton level in field theory. © 1998 Elsevier Science B.V.
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Stephen G. Naculich et al.

Oneinstanton predictions of SeibergWitten curves for product groups
https://digitalcommons.bowdoin.edu/physicsfacultypublications/149
https://digitalcommons.bowdoin.edu/physicsfacultypublications/149
Thu, 11 May 2023 12:58:32 PDT
Oneinstanton predictions for the prepotential are obtained from the SeibergWitten curve for the Coulomb branch of script N sign = 2 supersymmetric gauge theory for the product group IIn=1m SU(Nn) with a massless matter hypermultiplet in the bifundamental representation (Nn,N̄n+1) of SU(Nn) × SU(Nn+1) for n = 1 to m  1, together with N0 and Nm+1 matter hypermultiplets in the fundamental representations of SU(N1) and SU(Nm) respectively. The derivation uses a generalization of the systematic perturbation expansion about a hyperelliptic curve developed by us in earlier work. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Isabel P. Ennes et al.

Oneinstanton predictions for nonhyperelliptic curves derived from Mtheory
https://digitalcommons.bowdoin.edu/physicsfacultypublications/150
https://digitalcommons.bowdoin.edu/physicsfacultypublications/150
Thu, 11 May 2023 12:58:32 PDT
Oneinstanton predictions are obtained from certain nonhyperelliptic SeibergWitten curves derived from Mtheory for N = 2 supersymmetric gauge theories. We consider SU(N1) × SU(N2) gauge theory with a hypermultiplet in the bifundamental representation together with hypermultiplets in the defining representations of SU(N1) and SU(N2). We also consider SU(N) gauge theory with a hypermultiplet in the symmetric or antisymmetric representation, together with hypermultiplets in the defining representation. The systematic perturbation expansion about a hyperelliptic curve together with the judicious use of an involution map for the curve of the product groups provide the principal tools of the calculations. © 1999 Elsevier Science B.V.
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Isabel P. Ennes et al.

Oneinstanton predictions of a seibergwitten curve from M theory: The symmetric representation of SU(N)
https://digitalcommons.bowdoin.edu/physicsfacultypublications/148
https://digitalcommons.bowdoin.edu/physicsfacultypublications/148
Thu, 11 May 2023 12:58:31 PDT
We consider N = 2 supersymmetric YangMills theories in four dimensions with gauge group SU(N) for N larger than 2. Using the cubic curve for a matter hypermultiplet transforming in the symmetric representation, obtained from M theory by Landsteiner and Lopez, we calculate the prepotential up to the oneinstanton correction. We treat the curve as being approximately hyperelliptic and perform a perturbation expansion for the SeibergWitten differential to get the oneinstanton contribution. We find that it reproduces the correct result for one loop, and we obtain the prediction for that curve for the oneinstanton correction term.
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Isabel P. Ennes et al.

Two antisymmetric hypermultiplets in N = 2 SU(N) gauge theory: SeibergWitten curve and Mtheory interpretation
https://digitalcommons.bowdoin.edu/physicsfacultypublications/147
https://digitalcommons.bowdoin.edu/physicsfacultypublications/147
Thu, 11 May 2023 12:58:30 PDT
The oneinstanton contribution to the prepotential for N = 2 supersymmetric gauge theories with classical groups exhibits a universality of form. We extrapolate the observed regularity to SU (N) gauge theory with two antisymmetric hypermultiplets and Nf ≤ 3 hypermultiplets in the defining representation. Using methods developed for the instanton expansion of nonhyperelliptic curves, we construct an effective quartic SeibergWitten curve that generates this oneinstanton prepotential. We then interpret this curve in terms of an Mtheoretic picture involving NS 5branes, D4branes, D6branes, and orientifold sixplanes, and show that for consistency, an infinite chain of 5branes and orientifold sixplanes is required, corresponding to a curve of infinite order. © 1999 Elsevier Science B.V. All rights reserved.
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Isabel P. Ennes et al.

Elliptic models and Mtheory
https://digitalcommons.bowdoin.edu/physicsfacultypublications/146
https://digitalcommons.bowdoin.edu/physicsfacultypublications/146
Thu, 11 May 2023 12:58:29 PDT
We give a unified analysis of fourdimensional elliptic models with N = 2 supersymmetry and a simple gauge group, and their relation to Mtheory. Explicit calculations of the SeibergWitten curves and the resulting oneinstanton prepotential are presented. The remarkable regularities that emerge are emphasized. In addition, we calculate the prepotential in the Coulomb phase of the (asymptoticallyfree) Sp(2N) gauge theory with Nf fundamental hypermultiplets of arbitrary mass. © 2000 Elsevier Science B.V. All rights reserved.
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Isabel P. Ennes et al.

Elliptic models, type IIB orientifolds, and the AdS/CFT correspondence
https://digitalcommons.bowdoin.edu/physicsfacultypublications/145
https://digitalcommons.bowdoin.edu/physicsfacultypublications/145
Thu, 11 May 2023 12:58:28 PDT
We analyze the large N supergravity descriptions of the class of type IIB models Tdual to elliptic type IIA brane configurations containing two orientifold 6planes and up to two NS 5branes. The Tdual IIB configurations contain N D3branes in the background of an orientifold 7plane and, in some models, a Z2 orbifold and/or D7branes, which give rise to fourdimensional N=2 (or N=4) gauge theories with at most two factors. We identify the chiral primary states of the supergravity theories, and match them to gauge invariant operators of the corresponding superconformal theories using Maldacena's duality. © 2000 Elsevier Science B.V.
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Isabel P. Ennes et al.