Bibliography

1. Birkhoff G. and MacLane S., A Survey of Modern Algebra, Macmillan, New York, 1977. 2. Fraleigh J. B. and Beauregard R. A., Addison-Wesley, Reading, 1995. 3. Lipschutz S., Theory and Problems of Linear Algebra, Schaum’s Outline Series, McGraw- Hill, New York, 1991. 4. Halmos P. R. Finite Dimensional Vector Spaces, Springer, Berlin, 1974. 5. Merzbacher E., Quantum Mechanics, John Wiley & Sons, New York, 1970.

279 Index

Abelian group, 5, 17, 29, 33, 68, 254 Antimatrix, 257, 259 axioms for, 66, 68 Augmented matrix, 76, 85, 90, properties of, 8 101, 109 under addition, 28 of consistent linear system, 85, 112 with respect to addition of matrices, 6, 7, 36 of homogeneous linear system, 177, 179 Addition of classes, 3 Autodualism, 157 Addition of cosets, 66 invariant, 269 Addition of linmaps, 68 Automorphism, 103, 159 Addition of matrices, 36 of a given algebraic structure, 228 Addition of matrix-columns, 7 Addition of vectors, 4, 5, 6, 8, 33, 68 Basis, 9, 32, 33, 36Ð38 Additive identity, 5 equivalent definitions of, 32 Additive inverse, 5, 7, 36 Basis diads, 275 Adjoint, 52, 127, 153, 255 in superspaces, 273 Adjoint matrices, 266 Basis eigenvector, 178 Adjoint operators, 147, 155, 156, 186, Basis invariant map, 149, 152 201, 256 Bessel’s inequality, 132, 134 basic operations with, 153 Bijection, 6, 16, 59, 61Ð63, 67, 71, 103, 116, definition of, 269 164, 171 in superspace, 157 basis-independent, 147 Algebra of antilinear operators, 261 between algebras, 187 Algebra of matrices, 40, 155 between superspaces, 266 Algebra with unity, 146 invariant, 157 of linear operators, 155 Bijective correspondence, 66 Algebraic multiplicities, 175, 176, 178, 179 Bijective linear operator, 228 sum of, 186 Bijective linmap, 63, 67 Algebraic operations, 145 Bijective map, 147, 157, 209, 228 Algebraic structures, 8, 65, 145, 146 Binary vector operation, 18 Analytic geometry, 6, 219 Biorthogonal bases, 165Ð170 Antilinear bijection, 150, 152, 266 Biorthogonal vectors (functionals), 164 basis-independent, 263 Biorthogonality, 164, 166 between unitary spaces, 157 definitions of, 169 invariant, 266 Bra, 171, 265, 268, 271, 272, 277 Antilinear map, 150, 255 of /s1 linearly dependent columns of the Antilinear operators, 254, 259 augmented matrix, 85, 90, 91, 109 applications of, 261 modified, 177 in Hartree-Bogolybov Theory, 261 of vectors, 82

281 282 Index

Canonical form, 145 Cosine rule, 12 of orthogonal matrices, 241Ð242 Covariant change of the representing of orthogonal operators, 211 row, 268 Cartesian plane, 6 Covariant unitary vector, 149, 263 Cartesian product, 247, 272 Covariant vector, 165, 166, 253, 265 of ordered pairs, 249 Cramer’s rule, 46, 47, 107 Cartesian tensors, 163 Cross product, 18, 21, 22 CauchyÐSchwarz inequality, 11, 134 symbolic determinant, 28 Centroid, 14 table, 21 Characteristic equation, 175Ð178 Chemical reactions, 173 Decomposition of the unity, 204 Class of orthogonally equivalent bases, 124 Derivative, 75 Class of orthonormal (unitary equivalent) Descartes (Cartesian) form, 198 bases, 130 Descartes square, 123 Class of unitary equivalent bases, 130 Determinants, 46 Classical adjoint, 127 of diagonal matrix, 54Ð55 Classical physics, 1, 145, 158, 173 multiplicative property of, 54 Closed operation, 4, 7 properties of, 45, 50 Codomain, 60, 61, 65, 68 of triangular block-matrix, 176 Coefficient matrix, 18, 79 of triangular matrix, 53Ð54 Cofactor, 49 Diads, 247, 270, 271 expansion, 51, 53 as operators, 272 Column-addition property, 56 representation, 275, 276 Column-interchange property, 49Ð50 as the tensor product of a ket and a bra, 272 Column matrices, 42 Diagonalizability of normal operators, Column space, 80, 86, 87 184, 186 Column-space criterion, 83 Diagonalizable operator, 186 Commutation of an operator Diagonalization of a complex matrix, 182 with its adjoint, 186 Diagonalization of quadratic forms, 218 Commutative algebra, 40 Diagonalization procedure Commutativity, 34, 123 in unitary spaces, 183 Complex conjugation, 152, 259, 266 Dihedral groups, 235, 238Ð239 of a matrix, 127, 155 Dimension, 33, 64, 67 Composition of mappings, 61 of a subspace and its orthocomplement, 142 Composition of two invariant dualisms, 152 theorem, 65, 83, 91, 104, 111 Conic sections (conics), 220 Dirac form of the inner product degenerate, 220 of kets, 265 nondegenerate, 220 Dirac notation, 127, 171, 252, 264, in standard position, 222, 223 265, 270 Conjugate isomorphism, 150 in Quantum Mechanics, 171, 268 Consistent linear systems, 111 Direct eigendecomposition, 180 Contraction, 122 Direct sum, 85 Contraction rule, 265 of eigenspaces, 180 Contragredient matrix, 124, 129, 166, 263 of irreducible representations, 198 Contravariant change of the representing of matrices, 196 column, 264 of two subspaces, 141 Contravariant unitary vector, 149, 164, 263 Directed line segment, 2, 15 Contravariant vectors, 158, 265 Direction cosines, 25 Coplanarity of three vectors, 24 Direction vector, 25 Coset, 59, 65 Disjoint classes of unitary equivalent Coset form solution, 109 bases, 129 Coset of reflections, 237 Distributivity with respect to addition, 34 Coset representative, 78 Distributivity with respect to the addition of Coset solution method, 113, 118 vectors, 123 Index 283

Domain, 60, 61, 65, 110 Electrical systems, 173 common, 68 Electrodynamics, 41 Dot-multiplication, 10 Electromagnetism, 21 table, 10 Electron orbits in atoms, 229 , 9, 10, 12, 17, 119 Elementary matrices, 93 characteristic properties of, 123 definition of, 94 coordinate definition of, 121 general form of, 94 properties of, 120, 122 Elementary row operations (eros), 85, 91 of two vectors, 1, 119, 121, 122 on the augmented matrix, 95 Double index notation, 243 Elementary vectors, 247Ð249, 270 Dual basis, 165, 264, 266 Ellipse, 220, 223, 224 Dual bra, 265 degenerate, 220, 221 Dual functional, 263 in standard position, 225 Dual operators, 266 Energy operator, 229 , 42, 263 Equivalence class, 4, 161 dimension of, 147 of equal vectors, 3, 8, 15 rule for writing operators in, 267 natural representative of, 6 second, 167 of equivalence relation, 61, 67 theory of, 168 of orthogonally equivalent bases, 124 Dual vector, 150, 255, 264, 266 of representing matrices, 183 Dualism, 148, 150Ð152, 157, 263, Equivalence relation, 3, 95, 124, 161 265, 267 Euclidean plane, 6 between superspaces, 266, 269 Euclidean spaces, 1, 123, 163 between unitary spaces, 150 complex, 130 theory of, 209 Economics, 2, 34, 173 Euclidean vector spaces, 17 Eigen decomposition, 200 Expectation value, 198 of the unity, 207 in Quantum Mechanics, 199 Eigen problem, 145, 173, 174, 177, 178 of linear operator, 174 Factor spaces, 247, 248 of normal operator, 207 Fourier coefficients, 133, 165, 261 Eigen projection operator, 207 in ON basis, 130 Eigen spectrum of a symmetric matrix, 215 Fourier expansion, 133, 148 Eigenbasis, 180Ð182 Fundamental formula of dualism, 148, 149, Eigenline, 210, 240, 241 spanned by an eigenvector, 212 151, 165, 255, 263, 265, 269 Eigenspaces, 173, 180, 185, 189 Fundamental theorem of algebra, 175 mutually orthogonal, 185, 188 Eigenspectrum, 196 GaussÐJordan modified (GJM) form, 18, Eigenvalue, 173, 174, 177, 179, 189 85, 86 degenerate, 175 GaussÐJordan modified (GJM) procedure, 19, distinct, 181, 189 91, 111, 117 of a real matrix, 180 General quadratic equation, 221 nondegenerate, 175 General solution of a linear system, 83, in polar form, 200 84, 118 spectrum, 194, 198, 201 in coset form, 85, 90, 91, 110 of a positive operator, 199 Generating set, 141 of a projection operator, 200 Generator relations, 238 Eigenvalues Genetics, 173 of Hermitian matrix, 215 Geometric multiplicity, 176, 178Ð180 of symmetric operator, 212 Geometrical vectors, 1 Eigenvectors, 173, 174 in a Euclidean plane, 2 normalized, 189 Geometry, 2, 173, 219 Electrical engineering, 219 GJ method, 55, 96, 101, 104, 105, 106, 108 284 Index

GJ reduced row-echelon form, 43, 76, 86, 92, Invariant isomorphism (isodualism), 153, 167, 95, 97 168, 267 of augmented matrix, 112 between superspaces, 170, 171, 268, 269 existence of, 99 Invariant subspace, 184, 185, 240 fundamental property of, 99, 112 Inverse antilinear dualism, 255 GramÐSchmidt orthonormalization procedure, Inverse ero, 93 130, 134, 136, 137, 142, 192, 216 Inverse image, 59, 61, 65, 67, 75 Group generators, 238 of free vector with respect to matrix Group of all automorphisms, 163, 196, 228 linmap, 79 Group of all real invertible matrices, 229 Inverse map, 61, 63, 66 Group table, 238 Inverse matrix, 53, 94 Group theory Inverse of unitary contragredient basic axioms of, 130 matrix, 194 Inversion, 241 Heisenberg, 2 Invertible matrix, 44, 55, 101, 158 , 127, 153 Invertible replacement matrix, 129, 157, Hermitian conjugate, 153 159Ð161, 165, 167 Hermitian matrix, 198 change of basis by, 159 Hermitian operators, 145, 198, 199, 201 Involution, 259 equivalent definitions of, 198 Involutive map, 156 product of, 199 Involutive operation, 41 , 2 Isodual operator, 268, 275 of square integrable real functions, 137 acting on an arbitrary bra, 271 Homogeneous linear system, 84, 179 definition of, 269 of m equations with n unknowns, 144 general definition in Dirac Hyperbola, 220, 223, 224, 226 notation, 268 degenerate, 220, 221 Isodualism, 171 in standard position, 227 between superspaces, 267, 269 Isometric map, 157 Idempotency, 201 Isometric operator, 194 Idempotent property, 200 , 150, 152 Identity maps, 61 Isomorphic map, 63 Identity matrix, 40, 94, 101 Isomorphism, 42, 62, 63, 67, 70, 71, 121, 150, Identity of scalar multiplication, 28Ð29 157, 168 Identity operator, 146, 199, 202, 204 between algebras, 156, 187, 200, 277 diad representation of, 274, 276 between domain and range, 110 Image, 60 between unitary spaces, 250 Inclusion relation between two subspaces, 155 between vector spaces, 67 Inconsistent system, 101 Injection, 61, 62 Inner product, 34, 122Ð124 Kernel, 18, 67, 144 between elementary vectors, 248, 249 of linmap, 59, 63, 65 bilinear, 123 Ket, 171, 264Ð266, 268, 271, 272 of bras, 265 KroneckerÐCapelli theorem, 101 in complex , 128 Kronecker delta symbol, 36 basic properties of, 255 Kronecker multiplication, 246 definition of, 127, 255 Kronecker product in real vector space, 123 of columns, 252 in superspace, 147 of matrices, 243, 244, 250Ð252 in tensor algebra, 265 of p rows and m columns, 254 of two vectors, 130, 133 of rectangular matrices, 246 in unitary spaces, 131 of representing rows, 253 vector space, 131, 132, 136, 141, 154 of square matrices, 246 in vector space of real polynomials, 136 of vectors, 247 Index 285

Laplace expansion, 48, 51, 52, 54, 57 of rotation with inversion, 242 Legendre equation, 136 size of, 35 Legendre , 136 subalgebra, 42 Legendre polynomials, 136, 137 Matrix-column, 6 normalized, 136, 137, 139 of Fourier coefficients, 263 Leksicography method, 244 Matrix multiplication, 39, 41, 53 Length (or norm) of vector, 10, 34, 121 linear properties of, 125 LIND test, 141 Matrix representation, 79 Lineal, 29 of linear operators, 257 Linear bijection, 150, 157 of the tensor product, 252 Linear combination, 8 Matrix-row, 6 of cosets, 67 Mechanical stress, 173 of standard basis vectors, 71 Mechanics, 21, 41 of two sets, 29 Minor matrix, 48 of two vector components, 9 Mixed tensor of the second order, 161 Linear dependence, 97 Mixed triple product, 21 Linear economic models, 2, 122 Mixed unitary tensor, 164 Linear functional, 42, 147, 148, 151, 153, 168, Modern physics, 2 255, 263 Multiplication (composition) of operators, Linear group, 44 145, 146 Linear independence, 97 Multiplication of a coset, 66 test for, 111, 180 Multiplication of a linmap with a scalar, 68 Linear mapping, 59, 62, 67, 79, 151 Multiplication of scalars with vectors, 68 Linear operator, 145, 146, 228, 249 Multiplicative unity, 146 in a finite-dimensional unitary space, 153 representation of, 183 N-vector, 33, 42, 219 Linear span, 29, 33, 77 Norm, 2, 122, 133 Linear systems, 2, 79, 90, 110, 122 in ON basis, 133 equivalent, 92 in inner-product vector spaces, 134 nonhomogeneous, 83 Linearity, 256 of vector, 127 Linearly dependent set, 30, 33 Norm-preserving map, 150, 152 of nonzero vectors, 30 Normal, 135 Linearly independent (LI) set, 31 normalized, 135, 138, 139 Linearly independent eigenvectors, 179, of a vector onto a subspace, 143 180, 182 Normal matrix, 188, 190 Linmap, 59, 62, 67, 145 Normal operator, 184, 191 defect (nullity) of, 64 in Descartes form, 199 elementary basis, 74 equivalent definitions of, 199 many-to-one, 59, 65 in polar form, 199 matrix representation of, 73 spectral form of, 207 one-to-one (1Ð1), 61 spectrum of, 186, 194 onto, 75 Operators, 145 Magnetic groups, 261 matrix representation of, 154 Magnitude of a vector, 122 positive, 199 Mappings, 60 in Quantum Mechanics, 199 general theory of, 59 Ordered set, 32 one-to-one (1Ð1), 61 Ort, 11, 271 Matrix, 35, 36, 176, 243 of eigenline, 242 algebra, 60, 68, 92 Orthocenter, 13 block diagonal, 197 Orthocomplements, 155, 185 diagonal, 40, 54, 55, 188, 200 Orthogonal (Cartesian) tensor of the second factor, 259, 260 order, 208 286 Index

Orthogonal diagonalization of symmetric Quadratic forms, 218, 219 matrices, 214 associated, 221, 223, 226 procedure for, 219 Quantum entanglement, 261 Orthogonal eigenline, 241 Quantum mechanics, 2, 127, 141, 145, 173, Orthogonal groups, 163, 208 199, 202, 219, 252, 265, 270 Orthogonal invariant plane, 241 formalism of, 200 Orthogonal matrices, 124, 228Ð230 of many particles, 247 canonical forms of, 242 Quantum numbers, 265 characteristic property of, 228 Quantum physics, 158 Orthogonal replacement matrices, 16, 124, Quantum statistical physics, 145, 199 162, 215 Quarks, 2 Orthogonal set of vectors, 132 Orthogonal similarity, 215 Range, 63, 110 Orthogonal sum, 141, 144, 185 of linmap, 59, 63 of eigenlines, 241 of mapping, 61 of subspaces, 141, 145 Rank, 80, 86, 87 Orthogonal tensor of the second order, 209 of linmap, 65 basic invariants of, 210 Ratio theorem, 13 Orthogonal unit vectors, 9, 21, 124 basis of, 121, 122, 124 Rectangular coordinate system, 5 Orthogonality condition, 135 Recurrence formula, 136 Orthogonally diagonalizable operators, 211 Reflections, 231, 241 Orthonormal (ON) basis, 9, 18, 124, 132, 137 Replacement matrix, 123, 161, 163, 166, 168 equivalent, 142 Replacement theorem, 31 Orthonormal (ON) eigenbasis, 184, 185, 191 Representation matrices, 276 existence of, 186 basic formula for, 188 of isodual partners, 268 Parabola, 220, 223, 224 Representation of diads, 272 degenerate, 220, 221 Representation of linmaps, 72 Parallelepiped, 23Ð24 Representation of tensor product of linear Parallelogram, 22 operators, 244 rule, 3 Representation of vector in chosen ON Parametric equations of line, 25, 26 basis, 276 Parseval’s identity, 130, 133, 259, 260, 276 Representation theory, 59, 67Ð69, 146 Partition, 61 illustration of, 72 Physical laws, 158 Representing columns of kets, 270 covariant formulation of, 158 Representing matrix, 72, 185 Physics, 2, 34, 43, 119, 136 general formula for, 154 Point-normal equation of plane, 27Ð28 Representing rows of bras, 270 Positive definiteness, 34, 123, 256 Reversal rule Preimage, 60, 65, 66 for matrix inverses, 44 subspace, 81 for transposes, 41 Premultiplication, 93 Right-handed coordinate system, 16 Product of diagonal matrices, 40 Right-handed system, 21 Product of elementary matrices, 55, 101 Rodrigues formula, 136, 137 Product of two commuting projection Rotation matrix, 231, 242 operators, 205 Rotational symmetry of atoms, 229 Product space, 248 Rotations, 229, 242 Projection operators, 145, 200, 271 with inversion of the axis of rotation, 242 addition, multiplication and subtraction, 203 Row-addition property, 56Ð57 difference of, 206 Row equivalence, 95 matrix of, 201 Row-exchange property, 53 properties which define, 201 Row-interchange property, 49, 52, 56 Pythagorean theorem, 131, 143 Row space, 86, 87 Index 287

Sarrus rule, 37, 49 Symmetric matrix, 42 Scalar, 122 Symmetric operator, 212, 213 Scalar function, 123 Symmetric tensors, 41 Scalar matrix, 40 Symmetry group of equilateral triangle, 239 Scalar-matrix product, 36 Symmetry group of square, 237 Scalar multiplication, 7, 8, 17, 29, 38 Symmetry groups of regular n-sided polygons, property, 54, 55Ð56 238Ð239 Scalar product of two vectors, 122 Symmetry transformations, 237 Scalar projection, 9, 11 Scalar-valued function, 147 Technology, 136 Schr¬odinger, 2 Tensor algebra, 7, 71 Section formula, 13 Tensor multiplication Semi-direct product of two cyclic subgroups, of covariant vector with contravariant 237, 238 vector, 265 Set of all cosets, 66 of vector spaces, 122 Set of all images, 61 Tensor product Set of all inverse images, 61, 116 axioms of, 250, 273 Set of all linear operators in a finite- basis dependent definition of, 250 dimensional unitary space, 145 equivalent definitions of, 248 Set of all real polynomials, 37 of linear operators, 249 Set of all symmetric matrices, 139Ð140 of matrix-column spaces, 122 Set of antilinear operators, 254 of two unitary spaces, 270 Set of skew-symmetric matrices, 140 of a unitary space and its dual, 247 Sets of vector spaces, 59 of a unitary space with itself m times, 253 Similarity transformation, 160Ð162, 175 of unitary space(s), 247Ð249 Sine rule, 23 with a contraction, 265 Single index notation, 244 Tensorial square of a unitary space, 252, 253 Singular (noninvertible) matrix, 55 Theory of elementary particles, 2 Skew-symmetry, 255 Theory of linear representation of groups, 244 Spanning set, 31, 65, 165 Theory of tensors, 122 Special theory of relativity, 2, 122 Trace, 40 Square block matrix, 243 of diad, 272 Square matrix, 40 Transition matrix, 193, 194 determinant of, 45 from standard basis to eigenbasis, 181 Standard basis, 34, 70, 74, 94, 124, 247 Transition operator, 162, 193 for the subspace of skew-symmetric Transpose of matrix, 41 matrices, 140 of cofactors, 53, 106, 127, 230 Standard inner product, 124, 125, 127, Transpose property, 49Ð52, 56 131, 156 Triangle inequality, 11 of vector space of real polynomials, 126 in inner-product vector spaces, 134 Standard model, 2 Triangle rule for the addition of vectors, 4, 17 Standard position, 223 Triangular block-matrix, 176 relative to the coordinate axes, 221 Triangular matrix, 40, 53Ð54 Statistical operators, 199 Trigonometric identity, 230 Statistics, 219 Trigonometry, 12 Subspaces, 29, 30, 64, 141, 143, 174 dimension of, 33 Unit direction vector, 25 direct sum of, 139, 140 Unit norm, 134, 135 in an inner-product vector space, 141 Unit vectors (orts), 9, 11, 134 orthocomplement of, 141 Unitary group, 164 of vector space, 139 Unitary matrix, 164, 188 Superconductivity, 261 characteristic criteria for, 192 Superspaces, 147, 156, 157, 168, 266Ð269, 273 definition of, 163 Surjection, 61, 62, 75 diagonal, 200 288 Index

Unitary operators, 145, 194 negative, 7 equivalent definitions of, 194 position, 6, 12Ð14 reducibility of, 197 Vector spaces, 1, 2, 42, 66, 68, 84, 254, 267 study of antilinear, 261 change of basis in, 163 Unitary replacement matrix, 129, 149, 150, complex, 2, 42, 127, 131, 156 163, 183, 263 of complex polynomials, 131 Unitary spaces, 130, 147, 156, 163, 165, 263 dimension of, 68, 70 infinite-dimensional, 199 generalized, 1 of linear functionals, 254 homomorphism of, 62, 168, 171 one-dimensional, 147 infinite dimensional, 126 theory of, 141 of linear functionals, 164 Unitary superspace of matrix columns, 1, 33 adjoining in, 157 of polynomials, 75 Unitary tensors, 253, 254 quotient, 59, 66, 67, 84 Unitary transition matrix, 193 real, 1, 8, 17, 28, 34, 42, 123 Unitary transition operator, 193 Vibrations, 173 of mechanical systems, 219 Vector equation of line, 25 Von Neumann, 2 Vector equation of plane, 26 Vectors, 1, 122, 133, 143 Zero matrix, 36, 40Ð41 angle between, 34 Zero operator, 195, 199, 202 change of representing Zero polynomial, 38 column of, 159 Zero vector, 5, 7, 32, 59, 63, 76, 132