3 * Interface to GiNaC's clifford algebra (Dirac gamma) objects. */
6 * GiNaC Copyright (C) 1999-2008 Johannes Gutenberg University Mainz, Germany
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
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14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
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20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #ifndef __GINAC_CLIFFORD_H__
24 #define __GINAC_CLIFFORD_H__
36 /** This class holds an object representing an element of the Clifford
37 * algebra (the Dirac gamma matrices). These objects only carry Lorentz
38 * indices. Spinor indices are hidden. A representation label (an unsigned
39 * 8-bit integer) is used to distinguish elements from different Clifford
40 * algebras (objects with different labels commutate). */
41 class clifford : public indexed
43 GINAC_DECLARE_REGISTERED_CLASS(clifford, indexed)
46 clifford(const ex & b, unsigned char rl = 0);
47 clifford(const ex & b, const ex & mu, const ex & metr, unsigned char rl = 0, int comm_sign = -1);
49 // internal constructors
50 clifford(unsigned char rl, const ex & metr, int comm_sign, const exvector & v, bool discardable = false);
51 clifford(unsigned char rl, const ex & metr, int comm_sign, std::auto_ptr<exvector> vp);
53 // functions overriding virtual functions from base classes
55 unsigned precedence() const { return 65; }
57 ex eval_ncmul(const exvector & v) const;
58 bool match_same_type(const basic & other) const;
59 ex thiscontainer(const exvector & v) const;
60 ex thiscontainer(std::auto_ptr<exvector> vp) const;
61 unsigned return_type() const { return return_types::noncommutative; }
62 return_type_t return_type_tinfo() const;
63 // non-virtual functions in this class
65 unsigned char get_representation_label() const { return representation_label; }
66 ex get_metric() const { return metric; }
67 virtual ex get_metric(const ex & i, const ex & j, bool symmetrised = false) const;
68 bool same_metric(const ex & other) const;
69 int get_commutator_sign() const { return commutator_sign; } //**< See the member variable commutator_sign */
71 inline size_t nops() const {return inherited::nops() + 1; }
72 ex op(size_t i) const;
73 ex & let_op(size_t i);
74 ex subs(const exmap & m, unsigned options = 0) const;
77 void do_print_dflt(const print_dflt & c, unsigned level) const;
78 void do_print_latex(const print_latex & c, unsigned level) const;
82 unsigned char representation_label; /**< Representation label to distinguish independent spin lines */
83 ex metric; /**< Metric of the space, all constructors make it an indexed object */
84 int commutator_sign; /**< It is the sign in the definition e~i e~j +/- e~j e~i = B(i, j) + B(j, i)*/
87 /** This class represents the Clifford algebra unity element. */
88 class diracone : public tensor
90 GINAC_DECLARE_REGISTERED_CLASS(diracone, tensor)
92 // non-virtual functions in this class
94 void do_print(const print_context & c, unsigned level) const;
95 void do_print_latex(const print_latex & c, unsigned level) const;
99 /** This class represents the Clifford algebra generators (units). */
100 class cliffordunit : public tensor
102 GINAC_DECLARE_REGISTERED_CLASS(cliffordunit, tensor)
104 // functions overriding virtual functions from base classes
106 bool contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const;
108 // non-virtual functions in this class
110 void do_print(const print_context & c, unsigned level) const;
111 void do_print_latex(const print_latex & c, unsigned level) const;
115 /** This class represents the Dirac gamma Lorentz vector. */
116 class diracgamma : public cliffordunit
118 GINAC_DECLARE_REGISTERED_CLASS(diracgamma, cliffordunit)
120 // functions overriding virtual functions from base classes
122 bool contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const;
124 // non-virtual functions in this class
126 void do_print(const print_context & c, unsigned level) const;
127 void do_print_latex(const print_latex & c, unsigned level) const;
131 /** This class represents the Dirac gamma5 object which anticommutates with
132 * all other gammas. */
133 class diracgamma5 : public tensor
135 GINAC_DECLARE_REGISTERED_CLASS(diracgamma5, tensor)
137 // functions overriding virtual functions from base classes
138 ex conjugate() const;
140 // non-virtual functions in this class
142 void do_print(const print_context & c, unsigned level) const;
143 void do_print_latex(const print_latex & c, unsigned level) const;
147 /** This class represents the Dirac gammaL object which behaves like
149 class diracgammaL : public tensor
151 GINAC_DECLARE_REGISTERED_CLASS(diracgammaL, tensor)
153 // functions overriding virtual functions from base classes
154 ex conjugate() const;
156 // non-virtual functions in this class
158 void do_print(const print_context & c, unsigned level) const;
159 void do_print_latex(const print_latex & c, unsigned level) const;
163 /** This class represents the Dirac gammaL object which behaves like
165 class diracgammaR : public tensor
167 GINAC_DECLARE_REGISTERED_CLASS(diracgammaR, tensor)
169 // functions overriding virtual functions from base classes
170 ex conjugate() const;
172 // non-virtual functions in this class
174 void do_print(const print_context & c, unsigned level) const;
175 void do_print_latex(const print_latex & c, unsigned level) const;
181 /** Check whether a given return_type_t object (as returned by return_type_tinfo()
182 * is that of a clifford object (with an arbitrary representation label).
184 * @param ti tinfo key */
185 inline bool is_clifford_tinfo(const return_type_t& ti)
187 return *(ti.tinfo) == typeid(clifford);
190 /** Create a Clifford unity object.
192 * @param rl Representation label
193 * @return newly constructed object */
194 ex dirac_ONE(unsigned char rl = 0);
196 /** Create a Clifford unit object.
198 * @param mu Index (must be of class varidx or a derived class)
199 * @param metr Metric (should be indexed, tensmetric or a derived class, or a matrix)
200 * @param rl Representation label
201 * @return newly constructed Clifford unit object */
202 ex clifford_unit(const ex & mu, const ex & metr, unsigned char rl = 0);
204 /** Create a Dirac gamma object.
206 * @param mu Index (must be of class varidx or a derived class)
207 * @param rl Representation label
208 * @return newly constructed gamma object */
209 ex dirac_gamma(const ex & mu, unsigned char rl = 0);
211 /** Create a Dirac gamma5 object.
213 * @param rl Representation label
214 * @return newly constructed object */
215 ex dirac_gamma5(unsigned char rl = 0);
217 /** Create a Dirac gammaL object.
219 * @param rl Representation label
220 * @return newly constructed object */
221 ex dirac_gammaL(unsigned char rl = 0);
223 /** Create a Dirac gammaR object.
225 * @param rl Representation label
226 * @return newly constructed object */
227 ex dirac_gammaR(unsigned char rl = 0);
229 /** Create a term of the form e_mu * gamma~mu with a unique index mu.
231 * @param e Original expression
232 * @param dim Dimension of index
233 * @param rl Representation label */
234 ex dirac_slash(const ex & e, const ex & dim, unsigned char rl = 0);
236 /** Calculate dirac traces over the specified set of representation labels.
237 * The computed trace is a linear functional that is equal to the usual
238 * trace only in D = 4 dimensions. In particular, the functional is not
239 * always cyclic in D != 4 dimensions when gamma5 is involved.
241 * @param e Expression to take the trace of
242 * @param rls Set of representation labels
243 * @param trONE Expression to be returned as the trace of the unit matrix */
244 ex dirac_trace(const ex & e, const std::set<unsigned char> & rls, const ex & trONE = 4);
246 /** Calculate dirac traces over the specified list of representation labels.
247 * The computed trace is a linear functional that is equal to the usual
248 * trace only in D = 4 dimensions. In particular, the functional is not
249 * always cyclic in D != 4 dimensions when gamma5 is involved.
251 * @param e Expression to take the trace of
252 * @param rll List of representation labels
253 * @param trONE Expression to be returned as the trace of the unit matrix */
254 ex dirac_trace(const ex & e, const lst & rll, const ex & trONE = 4);
256 /** Calculate the trace of an expression containing gamma objects with
257 * a specified representation label. The computed trace is a linear
258 * functional that is equal to the usual trace only in D = 4 dimensions.
259 * In particular, the functional is not always cyclic in D != 4 dimensions
260 * when gamma5 is involved.
262 * @param e Expression to take the trace of
263 * @param rl Representation label
264 * @param trONE Expression to be returned as the trace of the unit matrix */
265 ex dirac_trace(const ex & e, unsigned char rl = 0, const ex & trONE = 4);
267 /** Bring all products of clifford objects in an expression into a canonical
268 * order. This is not necessarily the most simple form but it will allow
269 * to check two expressions for equality. */
270 ex canonicalize_clifford(const ex & e);
272 /** Automorphism of the Clifford algebra, simply changes signs of all
274 ex clifford_prime(const ex & e);
276 /** Main anti-automorphism of the Clifford algebra: makes reversion
277 * and changes signs of all clifford units. */
278 inline ex clifford_bar(const ex & e) { return clifford_prime(e.conjugate()); }
280 /** Reversion of the Clifford algebra, coincides with the conjugate(). */
281 inline ex clifford_star(const ex & e) { return e.conjugate(); }
283 /** Replaces dirac_ONE's (with a representation_label no less than rl) in e with 1.
284 * For the default value rl = 0 remove all of them. Aborts if e contains any
285 * clifford_unit with representation_label to be removed.
287 * @param e Expression to be processed
288 * @param rl Value of representation label
289 * @param options Defines some internal use */
290 ex remove_dirac_ONE(const ex & e, unsigned char rl = 0, unsigned options = 0);
292 /** Returns the maximal representation label of a clifford object
293 * if e contains at least one, otherwise returns -1
295 * @param e Expression to be processed
296 * @ignore_ONE defines if clifford_ONE should be ignored in the search*/
297 char clifford_max_label(const ex & e, bool ignore_ONE = false);
299 /** Calculation of the norm in the Clifford algebra. */
300 ex clifford_norm(const ex & e);
302 /** Calculation of the inverse in the Clifford algebra. */
303 ex clifford_inverse(const ex & e);
305 /** List or vector conversion into the Clifford vector.
307 * @param v List or vector of coordinates
308 * @param mu Index (must be of class varidx or a derived class)
309 * @param metr Metric (should be indexed, tensmetric or a derived class, or a matrix)
310 * @param rl Representation label
311 * @param e Clifford unit object
312 * @return Clifford vector with given components */
313 ex lst_to_clifford(const ex & v, const ex & mu, const ex & metr, unsigned char rl = 0);
314 ex lst_to_clifford(const ex & v, const ex & e);
316 /** An inverse function to lst_to_clifford(). For given Clifford vector extracts
317 * its components with respect to given Clifford unit. Obtained components may
318 * contain Clifford units with a different metric. Extraction is based on
319 * the algebraic formula (e * c.i + c.i * e)/ pow(e.i, 2) for non-degenerate cases
320 * (i.e. neither pow(e.i, 2) = 0).
322 * @param e Clifford expression to be decomposed into components
323 * @param c Clifford unit defining the metric for splitting (should have numeric dimension of indices)
324 * @param algebraic Use algebraic or symbolic algorithm for extractions
325 * @return List of components of a Clifford vector*/
326 lst clifford_to_lst(const ex & e, const ex & c, bool algebraic=true);
328 /** Calculations of Moebius transformations (conformal map) defined by a 2x2 Clifford matrix
329 * (a b\\c d) in linear spaces with arbitrary signature. The expression is
330 * (a * x + b)/(c * x + d), where x is a vector build from list v with metric G.
331 * (see Jan Cnops. An introduction to {D}irac operators on manifolds, v.24 of
332 * Progress in Mathematical Physics. Birkhauser Boston Inc., Boston, MA, 2002.)
334 * @param a (1,1) entry of the defining matrix
335 * @param b (1,2) entry of the defining matrix
336 * @param c (2,1) entry of the defining matrix
337 * @param d (2,2) entry of the defining matrix
338 * @param v Vector to be transformed
339 * @param G Metric of the surrounding space, may be a Clifford unit then the next parameter is ignored
340 * @param rl Representation label
341 * @return List of components of the transformed vector*/
342 ex clifford_moebius_map(const ex & a, const ex & b, const ex & c, const ex & d, const ex & v, const ex & G, unsigned char rl = 0);
344 /** The second form of Moebius transformations defined by a 2x2 Clifford matrix M
345 * This function takes the transformation matrix M as a single entity.
347 * @param M the defining matrix
348 * @param v Vector to be transformed
349 * @param G Metric of the surrounding space, may be a Clifford unit then the next parameter is ignored
350 * @param rl Representation label
351 * @return List of components of the transformed vector*/
352 ex clifford_moebius_map(const ex & M, const ex & v, const ex & G, unsigned char rl = 0);
356 #endif // ndef __GINAC_CLIFFORD_H__