Gukov, Sergei

Combined from CaltechAUTHORS

• Gukov, Sergei and Seong, Rak-Kyeong (2024) Machine learning BPS spectra and the gap conjecture; Physical Review D; Vol. 110; No. 4; 046016; 10.1103/physrevd.110.046016
• Gukov, Sergei and Halverson, James, et el. (2024) Rigor with machine learning from field theory to the Poincaré conjecture; Nature Reviews Physics; 10.1038/s42254-024-00709-0
• Collins, Tristan C. and Gukov, Sergei, et el. (2023) Special Lagrangian Cycles and Calabi-Yau Transitions; Communications in Mathematical Physics; 10.1007/s00220-023-04655-3
• Costantino, Francesco and Gukov, Sergei, et el. (2023) Non-Semisimple TQFT's and BPS q-Series; Symmetry, Integrability and Geometry, Methods and Applications (SIGMA); Vol. 19; Art. No. 10; 10.3842/sigma.2023.010
• Gukov, Sergei and Lee, Vincent S. H., et el. (2023) Near-horizon quantum dynamics of 4D Einstein gravity from 2D Jackiw-Teitelboim gravity; Physical Review D; Vol. 107; No. 1; Art. No. 016004; 10.1103/physrevd.107.016004
• Ekholm, Tobias and Gruen, Angus, et el. (2022) Ẑ at Large N: From Curve Counts to Quantum Modularity; Communications in Mathematical Physics; 10.1007/s00220-022-04469-9
• Gukov, Sergei and Lee, Vincent S. H., et el. (2022) Near-Horizon Quantum Dynamics of 4-d Einstein Gravity from 2-d JT Gravity; 10.48550/arXiv.2205.02233
• Ekholm, Tobias and Gruen, Angus, et el. (2022) Branches, quivers, and ideals for knot complements; Journal of Geometry and Physics; Vol. 177; Art. No. 104520; 10.1016/j.geomphys.2022.104520
• Gukov, Sergei and Pei, Du, et el. (2021) Symmetries of 2d TQFTs and Equivariant Verlinde Formulae for General Groups
• Gukov, Sergei and Park, Sunghyuk, et el. (2021) Cobordism Invariants from BPS q-Series; Annales Henri Poincaré; Vol. 22; No. 12; 4173-4203; 10.1007/s00023-021-01089-2
• Gukov, Sergei and Hsin, Po-Shen, et el. (2021) Rozansky-Witten geometry of Coulomb branches and logarithmic knot invariants; Journal of Geometry and Physics; Vol. 168; Art. No. 104311; 10.1016/j.geomphys.2021.104311
• Gukov, Sergei and Halverson, James, et el. (2021) Learning to unknot; Machine Learning: Science and Technology; Vol. 2; No. 2; Art. No. 025035; 10.1088/2632-2153/abe91f
• Gukov, Sergei and Pei, Du, et el. (2021) 4-manifolds and topological modular forms; Journal of High Energy Physics; Vol. 2021; No. 5; Art. No. 84; 10.1007/JHEP05(2021)084
• Gukov, Sergei and Hsin, Po-Shen, et el. (2021) Generalized global symmetries of T[M] theories. Part I; Journal of High Energy Physics; Vol. 2021; No. 4; Art. No. 232; 10.1007/JHEP04(2021)232
• Gukov, Sergei and Manolescu, Ciprian (2021) A two-variable series for knot complements; Quantum Topology; Vol. 12; No. 1; 1-109; 10.4171/QT/145
• Franco, Sebastián and Gukov, Sergei, et el. (2020) "Lagrangian disks" in M-theory; Journal of High Energy Physics; Vol. 2020; No. 11; Art. No. 33; 10.1007/jhep11(2020)033
• Dedushenko, Mykola and Gukov, Sergei, et el. (2020) 3d TQFTs from Argyres–Douglas theories; Journal of Physics A: Mathematical and General; Vol. 53; No. 43; Art. No. 43LT01; 10.1088/1751-8121/abb481
• Chun, Sungbong and Gukov, Sergei, et el. (2020) 3d-3d correspondence for mapping tori; Journal of High Energy Physics; Vol. 2020; No. 9; Art. No. 152; 10.1007/jhep09(2020)152
• Gukov, Sergei and Pei, Du, et el. (2020) Trialities of minimally supersymmetric 2d gauge theories; Journal of High Energy Physics; Vol. 2020; No. 4; Art. No. 079; 10.1007/JHEP04(2020)079
• Gukov, Sergei and Pei, Du, et el. (2020) BPS spectra and 3-manifold invariants; Journal of Knot Theory and its Ramifications; Vol. 29; No. 2; Art. No. 2040003; 10.1142/S0218216520400039
• Feigin, Boris and Gukov, Sergei (2020) VOA[M₄]; Journal of Mathematical Physics; Vol. 61; No. 1; Art. No. 012302; 10.1063/1.5100059
• Gadde, Abhijit and Gukov, Sergei, et el. (2019) Exact Solutions of 2d Supersymmetric Gauge Theories; Journal of High Energy Physics; Vol. 2019; No. 11; Art. No. 174; 10.1007/JHEP11(2019)174
• Cheng, Miranda C. N. and Chun, Sungbong, et el. (2019) 3d modularity; Journal of High Energy Physics; Vol. 2019; No. 10; Art. No. 10; 10.1007/jhep10(2019)010
• Dedushenko, Mykola and Gukov, Sergei (2019) IR duality in 2D N = (0,2) gauge theory with noncompact dynamics; Physical Review D; Vol. 99; No. 6; Art. No. 066005; 10.1103/PhysRevD.99.066005
• Gorsky, Eugene and Gukov, Sergei, et el. (2018) Quadruply-graded colored homology of knots; Fundamenta Mathematicae; Vol. 243; 209-299; 10.4064/fm30-11-2017
• Gukov, Sergei and Pei, Du, et el. (2018) Equivariant Verlinde algebra from superconformal index and Argyres-Seiberg duality; Communications in Mathematical Physics; Vol. 357; No. 3; 1215-1251; 10.1007/s00220-017-3074-8
• Gukov, Sergei (2017) Trisecting non-Lagrangian theories; Journal of High Energy Physics; Vol. 2017; No. 11; Art. No. 178; 10.1007/JHEP11(2017)178
• Gukov, Sergei and Pei, Du (2017) Equivariant Verlinde formula from fivebranes and vortices; Communications in Mathematical Physics; Vol. 355; No. 1; 1-50; 10.1007/s00220-017-2931-9
• Gukov, Sergei and Putrov, Pavel, et el. (2017) Fivebranes and 3-manifold homology; Journal of High Energy Physics; Vol. 2017; No. 07; Art. No. 071; 10.1007/JHEP07(2017)071
• Gukov, Sergei and Liu, Chiu-Chu Melissa, et el. (2017) On topological approach to local theory of surfaces in Calabi–Yau threefolds; Advances in Theoretical and Mathematical Physics; Vol. 21; No. 7; 1679-1728; 10.4310/ATMP.2017.v21.n7.a4
• Gukov, Sergei (2017) RG Flows and Bifurcations; Nuclear Physics B; Vol. 919; 583-638; 10.1016/j.nuclphysb.2017.03.025
• Dedushenko, Mykola and Gukov, Sergei, et el. (2017) Vertex algebras and 4-manifold invariants; 10.48550/arXiv.1705.01645
• Gadde, Abhijit and Gukov, Sergei, et el. (2016) Fivebranes and 4-Manifolds; ISBN 978-3-319-43646-3; Arbeitstagung Bonn 2013; 155-245; 10.1007/978-3-319-43648-7_7
• Andersen, Jørgen Ellegaard and Gukov, Sergei, et el. (2016) The Verlinde formula for Higgs bundles; 10.48550/arXiv.1608.01761
• Gukov, Sergei and Marino, Marcos, et el. (2016) Resurgence in complex Chern-Simons theory; 10.48550/arXiv.1605.07615
• Gukov, Sergei and Walcher, Johannes (2016) Matrix Factorizations and Kauffman Homology; 10.48550/arXiv.0512298
• Gukov, Sergei and Martinec, Emil, et el. (2016) Chern-Simons Gauge Theory and the AdS_3/CFT_2 Correspondence; 10.48550/arXiv.0403225
• Gukov, Sergei and Martinec, Emil, et el. (2016) An Index for 2D field theories with large N=4 superconformal symmetry; 10.48550/arXiv.0404023
• Gukov, Sergei and Kapustin, Anton (2016) Topological Quantum Field Theory, Nonlocal Operators, and Gapped Phases of Gauge Theories; 10.48550/arXiv.1307.4793
• Gadde, Abhijit and Gukov, Sergei, et el. (2016) Duality Defects; 10.48550/arXiv.1404.2929
• Chung, Hee-Joong and Dimofte, Tudor, et el. (2016) 3d-3d Correspondence Revisited; Journal of High Energy Physics; Vol. 2016; No. 4; Art. No. 140; 10.1007/JHEP04(2016)140
• Gukov, Sergei and Nawata, Satoshi, et el. (2016) Sequencing BPS Spectra; Journal of High Energy Physics; Vol. 2016; No. 03; Art. No. 004; 10.1007/JHEP03(2016)004
• Elliot, Ross and Gukov, Sergei (2016) Exceptional knot homology; Journal of Knot Theory and its Ramifications; Vol. 25; No. 3; Art. No. 1640003; 10.1142/S0218216516400034
• Frenkel, Edward and Gukov, Sergei, et el. (2016) Surface operators and separation of variables; Journal of High Energy Physics; Vol. 2016; No. 1; Art. No. 179; 10.1007/JHEP01(2016)179
• Gukov, Sergei (2016) Counting RG flows; Journal of High Energy Physics; Vol. 2016; No. 1; Art. No. 020; 10.1007/JHEP01(2016)020
• Gukov, Sergei and Saberi, Ingmar (2016) Lectures on Knot Homology and Quantum Curves; ISBN 978-1-4704-1459-7; Physics and Mathematics of Link Homology; 59-97; 10.1090/conm/680/13700
• Chun, Sungbong and Gukov, Sergei, et el. (2015) Junctions of surface operators and categorification of quantum groups; 10.48550/arXiv.1507.06318
• Gukov, Sergei (2015) Surface Operators; ISBN 978-3-319-18768-6; New Dualities of Supersymmetric Gauge Theories; 223-259; 10.1007/978-3-319-18769-3_8
• Gukov, Sergei and Sułkowski, Piotr (2014) A-Polynomial, B-Model, and Quantization; ISBN 978-3-319-06513-7; Homological Mirror Symmetry and Tropical Geometry; 87-151; 10.1007/978-3-319-06514-4_4
• Gadde, Abhijit and Gukov, Sergei, et el. (2014) Walls, lines, and spectral dualities in 3d gauge theories; Journal of High Energy Physics; Vol. 2014; No. 5; Art. No. 47; 10.1007/JHEP05(2014)047
• Gadde, Abhijit and Gukov, Sergei (2014) 2d index and surface operators; Journal of High Energy Physics; Vol. 2014; No. 3; Art. No. 80; 10.1007/JHEP03(2014)080
• Gadde, Abhijit and Gukov, Sergei, et el. (2014) (0, 2) trialities; Journal of High Energy Physics; Vol. 2014; No. 3; Art. No. 76; 10.1007/JHEP03(2014)076
• Dimofte, Tudor and Gaiotto, Davide, et el. (2014) Gauge Theories Labelled by Three-Manifolds; Communications in Mathematical Physics; Vol. 325; No. 2; 367-419; 10.1007/s00220-013-1863-2
• Gaiotto, Davide and Gukov, Sergei, et el. (2013) Surface defects and resolvents; Journal of High Energy Physics; Vol. 2013; No. 9; Art. No. 70; 10.1007/JHEP09(2013)070
• Dimofte, Tudor and Gukov, Sergei (2013) Chern-Simons theory and S-duality; Journal of High Energy Physics; Vol. 2013; No. 5; Art. No. 109; 10.1007/JHEP05(2013)109
• Fuji, Hiroyuki and Gukov, Sergei, et el. (2013) Super-A-polynomial for knots and BPS states; Nuclear Physics B; Vol. 867; No. 2; 506-546; 10.1016/j.nuclphysb.2012.10.005
• Fuji, Hiroyuki and Gukov, Sergei, et el. (2013) 3d analogs of Argyres-Douglas theories and knot homologies; Journal of High Energy Physics; Vol. 2013; No. 1; Art. No. 175; 10.1007/JHEP01(2013)175
• Dimofte, Tudor and Gaiotto, Davide, et el. (2013) 3-Manifolds and 3d indices; Advances in Theoretical and Mathematical Physics; Vol. 17; No. 5; 975-1076; 10.4310/ATMP.2013.v17.n5.a3
• Gukov, Sergei and Sułkowski, Piotr (2012) A-polynomial, B-model, and quantization; Journal of High Energy Physics; Vol. 2012; No. 2; Art. No. 070; 10.1007/JHEP02(2012)070
• Gukov, Sergei and Stošić, Marko (2012) Homological algebra of knots and BPS states; ISBN 9780821872956; String-Math 2011; 125-171; 10.1090/pspum/085
• Fuji, Hiroyuki and Gukov, Sergei, et el. (2012) Volume conjecture: refined and categorified; Advances in Theoretical and Mathematical Physics; Vol. 16; No. 6; 1669-1777; 10.48550/arXiv.1203.2182
• Dimofte, Tudor and Gukov, Sergei, et el. (2011) Vortex Counting and Lagrangian 3-Manifolds; Letters in Mathematical Physics; Vol. 98; No. 3; 225-287; 10.1007/s11005-011-0531-8
• Gukov, Sergei (2011) Quantization via mirror symmetry; Japanese Journal of Mathematics; Vol. 6; No. 2; 65-119; 10.1007/s11537-011-1033-2
• Dimofte, Tudor and Gukov, Sergei, et el. (2011) Quantum Wall Crossing in N=2 Gauge Theories; Letters in Mathematical Physics; Vol. 95; No. 1; 1-25; 10.1007/s11005-010-0437-x
• Dimofte, Tudor and Gukov, Sergei (2011) Quantum Field Theory and the Volume Conjecture; ISBN 978-0-8218-4960-6; Interactions between hyperbolic geometry, quantum topology, and number theory; 41-67; 10.1090/conm/541/10678
• Gukov, Sergei and Iqbal, Amer, et el. (2010) Link Homologies and the Refined Topological Vertex; Communications in Mathematical Physics; Vol. 298; No. 3; 757-785; 10.1007/s00220-010-1045-4
• Dimofte, Tudor and Gukov, Sergei (2010) Refined, Motivic, and Quantum; Letters in Mathematical Physics; Vol. 91; No. 1; 1-27; 10.1007/s11005-009-0357-9
• Gukov, Sergei and Witten, Edward (2010) Rigid Surface Operators; Advances in Theoretical and Mathematical Physics; Vol. 14; No. 1; 87-178; 10.4310/ATMP.2010.v14.n1.a3
• Alday, Luis F. and Gaiotto, Davide, et el. (2010) Loop and surface operators in N = 2 gauge theory and Liouville modular geometry; Journal of High Energy Physics; Vol. 2010; No. 1; Art. No. 113; 10.1007/JHEP01(2010)113
• Gukov, Sergei and Witten, Edward (2009) Branes and quantization; Advances in Theoretical and Mathematical Physics; Vol. 13; No. 5; 1445-1518; 10.4310/ATMP.2009.v13.n5.a5
• Gukov, Sergei (2009) Surface Operators and Knot Homologies; ISBN 978-90-481-2809-9; New Trends in Mathematical Physics; 313-343; 10.1007/978-90-481-2810-5_22
• Dimofte, Tudor and Gukov, Sergei, et el. (2009) Exact Results for Perturbative Chern-Simons Theory with Complex Gauge Group; Communications in Number Theory and Physics; Vol. 3; No. 2; 363-443; 10.4310/CNTP.2009.v3.n2.a4
• Gukov, Sergei and Murakami, Hitoshi (2008) SL(2,C) Chern–Simons Theory and the Asymptotic Behavior of the Colored Jones Polynomial; Letters in Mathematical Physics; Vol. 86; No. 2-3; 79-98; 10.1007/s11005-008-0282-3
• Gukov, Sergei and Witten, Edward (2008) Gauge Theory, Ramification, And The Geometric Langlands Program; Current Developments in Mathematics; Vol. 2006; 35-180; 10.4310/CDM.2006.v2006.n1.a2
• Gaberdiel, Matthias R. and Gukov, Sergei, et el. (2008) Extremal N = (2, 2) 2D Conformal Field Theories and Constraints of Modularity; Communications in Number Theory and Physics; Vol. 2; No. 4; 743-801; 10.4310/CNTP.2008.v2.n4.a3
• Gukov, Sergei and Motl, Luboš, et el. (2007) Equivalence of twistor prescriptions for super Yang-Mills; Advances in Theoretical and Mathematical Physics; Vol. 11; No. 2; 199-231; 10.4310/ATMP.2007.v11.n2.a1
• Gukov, Sergei and Saraikin, Kirill, et el. (2006) Stringy wave function for an S^3 cosmology; Physical Review D; Vol. 73; No. 6; Art. No. 066009; 10.1103/PhysRevD.73.066009
• Gukov, Sergei and Saraikin, Kirill, et el. (2006) Entropic principle and asymptotic freedom; Physical Review D; Vol. 73; No. 6; Art. No. 066010; 10.1103/PhysRevD.73.066010
• Dunfield, Nathan M. and Gukov, Sergei, et el. (2006) The Superpolynomial for Knot Homologies; Experimental Mathematics; Vol. 15; No. 2; 129-159; 10.1080/10586458.2006.10128956
• Gukov, Sergei and Schwarz, Albert, et el. (2005) Khovanov-Rozansky Homology and Topological Strings; Letters in Mathematical Physics; Vol. 74; No. 1; 53-74; 10.1007/s11005-005-0008-8
• Dijkgraaf, Robbert and Gukov, Sergei, et el. (2005) Topological M-theory as Unification of Form Theories of Gravity; Advances in Theoretical and Mathematical Physics; Vol. 9; No. 4; 603-665; 10.4310/ATMP.2005.v9.n4.a5
• Gukov, Sergei and Martinec, Emil, et el. (2005) Search for a holographic dual to AdS_3 x S^3 x S^3 x S^1; Advances in Theoretical and Mathematical Physics; Vol. 9; No. 3; 435-525; 10.4310/ATMP.2005.v9.n3.a3
• Gukov, Sergei (2005) Three-Dimensional Quantum Gravity, Chern-Simons Theory, and the A-Polynomial; Communications in Mathematical Physics; Vol. 255; No. 3; 577-627; 10.1007/s00220-005-1312-y
• Gukov, Sergei and Kachru, Shamit, et el. (2004) Heterotic moduli stabilization with fractional Chern-Simons invariants; Physical Review D; Vol. 69; No. 8; Art. No. 086008; 10.1103/PhysRevD.69.086008
• Gukov, Sergei and Vafa, Cumrun (2004) Rational Conformal Field Theories and Complex Multiplication; Communications in Mathematical Physics; Vol. 246; No. 1; 181-210; 10.1007/s00220-003-1032-0
• Acharya, Bobby S. and Gukov, Sergei (2004) M theory and singularities of exceptional holonomy manifolds; Physics Reports; Vol. 392; No. 3; 121-189; 10.1016/j.physrep.2003.10.017
• Gukov, Sergei and Takayanagi, Tadashi, et el. (2004) Flux backgrounds in 2D string theory; Journal of High Energy Physics; Vol. 2004; No. 3; Art. No. 017; 10.1088/1126-6708/2004/03/017
• Dijkgraaf, Robbert and Gukov, Sergei, et el. (2003) Perturbative analysis of gauged matrix models; Physical Review D; Vol. 68; No. 4; Art. No. 045007; 10.1103/PhysRevD.68.045007
• Gukov, Sergei and Sparks, James, et el. (2003) Conifold transitions and five-brane condensation in M-theory on Spin(7) manifolds; Classical and Quantum Gravity; Vol. 20; No. 4; 665-705; 10.1088/0264-9381/20/4/306
• Gukov, Sergei and Yau, Shing-Tung, et el. (2003) Duality and Fibrations on G_2 Manifolds; Turkish Journal of Mathematics; Vol. 27; No. 1; 61-97; 10.48550/arXiv.0203217v1
• Gukov, Sergei and Tong, David (2002) D-brane probes of G_2 holonomy manifolds; Physical Review D; Vol. 66; No. 8; Art. No. 087901; 10.1103/PhysRevD.66.087901
• Gukov, Sergei and Haack, Michael (2002) IIA string theory on Calabi-Yau fourfolds with background fluxes; Nuclear Physics B; Vol. 639; No. 1-2; 95-128; 10.1016/S0550-3213(02)00442-X
• Acharya, Bobby S. and De La Ossa, Xenia, et el. (2002) G-flux, supersymmetry and Spin(7) manifolds; Journal of High Energy Physics; Vol. 2002; No. 9; Art. No. 047; 10.1088/1126-6708/2002/09/047
• Gukov, Sergei and Tong, David (2002) D-Brane probes of Special Holonomy Manifolds, and Dynamics of N=1 Three-Dimensional Gauge Theories; Journal of High Energy Physics; Vol. 2002; No. 4; Art. No. 50; 10.1088/1126-6708/2002/04/050
• Gukov, Sergei and Sparks, James (2002) M-theory on Spin(7) manifolds; Nuclear Physics B; Vol. 625; No. 1-2; 3-69; 10.1016/S0550-3213(02)00018-4
• Berkovits, Nathan and Gukov, Sergei, et el. (2001) Superstrings in 2D backgrounds with R–R flux and new extremal black holes; Nuclear Physics B; Vol. 614; No. 1-2; 195-232; 10.1016/S0550-3213(01)00413-8
• Brandhuber, Andreas and Gomis, Jaume, et el. (2001) Gauge theory at large N and new G₂ holonomy metrics; Nuclear Physics B; Vol. 611; No. 1-3; 179-204; 10.1016/S0550-3213(01)00340-6
• Gubser, S. S. and Gukov, S., et el. (2001) The Hagedorn transition in noncommutative open string theory; Journal of Mathematical Physics; Vol. 42; No. 7; 2749-2764; 10.1063/1.1372176
• Behrndt, Klaus and Gukov, Sergei, et el. (2001) Domain walls, black holes, and supersymmetric quantum mechanics; Nuclear Physics B; Vol. 601; No. 1-2; 49-76; 10.1016/S0550-3213(01)00052-9
• Gates, S. James, Jr. and Gukov, Sergei, et el. (2000) Two two-dimensional supergravity theories from Calabi–Yau four-folds; Nuclear Physics B; Vol. 584; No. 1-2; 109-148; 10.1016/S0550-3213(00)00374-6
• Behrndt, Klaus and Gukov, Sergei (2000) Domain walls and superpotentials from M-theory on Calabi-Yau three-folds; Nuclear Physics B; Vol. 580; No. 1-2; 225-242; 10.1016/S0550-3213(00)00149-8
• Gukov, Sergei and Periwal, Vipul (2000) Dbrane phase transitions and monodromy in K-theory; Journal of Geometry and Physics; Vol. 34; No. 3-4; 263-269; 10.1016/S0393-0440(99)00067-4
• Gukov, Sergei (2000) Solitons, superpotentials and calibrations; Nuclear Physics B; Vol. 574; No. 1-2; 169-188; 10.1016/S0550-3213(00)00053-5
• Gukov, Sergei (2000) K-Theory, Reality, and Orientifolds; Communications in Mathematical Physics; Vol. 210; No. 3; 621-639; 10.1007/s002200050793
• Gukov, Sergei and Kapustin, Anton (1999) New N = 2 superconformal field theories from M/F-theory orbifolds; Nuclear Physics B; Vol. 545; No. 1-3; 283-308; 10.1016/S0550-3213(99)00008-5
• Diaconescu, Duiliu-Emanuel and Gukov, Sergei (1998) Three-dimensional N = 2 gauge theories and degenerations of Calabi-Yau four-folds; Nuclear Physics B; Vol. 535; No. 1-2; 171-196; 10.1016/S0550-3213(98)00597-5
• Gukov, Sergei and Rangamani, Mukund, et el. (1998) Dibaryons, branes, and strings in AdS orbifold models; Journal of High Energy Physics; Vol. 1998; No. 12; Art. No. 025; 10.1088/1126-6708/1998/12/025
• Gukov, Sergei (1998) Comments on N = S AdS orbifolds; Physics Letters B; Vol. 439; No. 1-2; 23-28; 10.1016/S0370-2693(98)01005-3
• Gukov, S. (1997) Supersymmetric spin glass; Journal of Experimental and Theoretical Physics Letters; Vol. 65; No. 8; 694-700; 10.1134/1.567408
• Gukov, Sergei and Polyubin, Igor (1997) Related N = 2 SUSY Yang Mills Theories and Instanton Expansion; Physics Letters B; Vol. 391; No. 1-2; 115-123; 10.1016/S0370-2693(96)01454-2