6,955 research outputs found
A computer algebra user interface manifesto
Many computer algebra systems have more than 1000 built-in functions, making
expertise difficult. Using mock dialog boxes, this article describes a proposed
interactive general-purpose wizard for organizing optional transformations and
allowing easy fine grain control over the form of the result even by amateurs.
This wizard integrates ideas including:
* flexible subexpression selection;
* complete control over the ordering of variables and commutative operands,
with well-chosen defaults;
* interleaving the choice of successively less main variables with applicable
function choices to provide detailed control without incurring a combinatorial
number of applicable alternatives at any one level;
* quick applicability tests to reduce the listing of inapplicable
transformations;
* using an organizing principle to order the alternatives in a helpful
manner;
* labeling quickly-computed alternatives in dialog boxes with a preview of
their results,
* using ellipsis elisions if necessary or helpful;
* allowing the user to retreat from a sequence of choices to explore other
branches of the tree of alternatives or to return quickly to branches already
visited;
* allowing the user to accumulate more than one of the alternative forms;
* integrating direct manipulation into the wizard; and
* supporting not only the usual input-result pair mode, but also the useful
alternative derivational and in situ replacement modes in a unified window.Comment: 38 pages, 12 figures, to be published in Communications in Computer
Algebr
A Recipe for Symbolic Geometric Computing: Long Geometric Product, BREEFS and Clifford Factorization
In symbolic computing, a major bottleneck is middle expression swell.
Symbolic geometric computing based on invariant algebras can alleviate this
difficulty. For example, the size of projective geometric computing based on
bracket algebra can often be restrained to two terms, using final polynomials,
area method, Cayley expansion, etc. This is the "binomial" feature of
projective geometric computing in the language of bracket algebra.
In this paper we report a stunning discovery in Euclidean geometric
computing: the term preservation phenomenon. Input an expression in the
language of Null Bracket Algebra (NBA), by the recipe we are to propose in this
paper, the computing procedure can often be controlled to within the same
number of terms as the input, through to the end. In particular, the
conclusions of most Euclidean geometric theorems can be expressed by monomials
in NBA, and the expression size in the proving procedure can often be
controlled to within one term! Euclidean geometric computing can now be
announced as having a "monomial" feature in the language of NBA.
The recipe is composed of three parts: use long geometric product to
represent and compute multiplicatively, use "BREEFS" to control the expression
size locally, and use Clifford factorization for term reduction and transition
from algebra to geometry.
By the time this paper is being written, the recipe has been tested by 70+
examples from \cite{chou}, among which 30+ have monomial proofs. Among those
outside the scope, the famous Miquel's five-circle theorem \cite{chou2}, whose
analytic proof is straightforward but very difficult symbolic computing, is
discovered to have a 3-termed elegant proof with the recipe
Spherical Universe topology and the Casimir effect
The mode problem on the factored 3--sphere is applied to field theory
calculations for massless fields of spin 0, 1/2 and 1. The degeneracies on the
factors, including lens spaces, are neatly derived in a geometric fashion.
Vacuum energies are expressed in terms of the polyhedral degrees and equivalent
expressions given using the cyclic decomposition of the covering group. Scalar
functional determinants are calculated and the spectral asymmetry function
treated by the same approach with explicit forms on one-sided lens spaces.Comment: 33 pages, 1 figure. Typos corrected and one reference adde
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