<A NAME=VECTOR>
<TITLE>VECTOR</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>
<B>VECTOR</B> _ _ _ _ _ _ _ _ _ _ _ _ <B>declaration</B><P>
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The <em>vector</em> declaration declares that its arguments are of type <em>vect
or</em>.
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syntax: </H3>
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<em>vector</em><identifier>{,<identifier>}*
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<identifier> must be a valid REDUCE identifier. It may have already been
used for a matrix, array, operator or scalar variable. After an identifier
has been declared to be a vector, it may not be used as a scalar variable.
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Vectors are special entities for high-energy physics calculations. You
cannot put values into their coordinates; they do not have coordinates.
They are legal arguments for the high-energy physics operators
<A HREF=r37_0410.html>eps</A>,
<A HREF=r37_0411.html>g</A> and <em>.</em> (dot). Vector variables are
used to represent gamma matrices and gamma matrices contracted with Lorentz
4-vectors, since there are no Dirac variables per se in the system.
Vectors do follow the usual vector rules for arithmetic operations:
<em>+</em> and <em>-</em> operate upon two or more vectors, producing a
vector; <em>*</em> and <em>/</em> cannot be used between vectors; the
scalar product is represented by the . operator; and the product of a
scalar and vector expression is well defined, and is a vector.
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You can represent components of vectors by including representations of unit
vectors in your system. For instance, letting <em>E0</em> represent the unit
vector (1,0,0,0), the command
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<em>V1.E0 := 0;</em>would set up the substitution of zero for the first componen
t of the vector
<em>V1</em>.
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Identifiers that are declared by the <em>index</em> and <em>mass</em> declaratio
ns are
automatically declared to be vectors.
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The following errors can occur in calculations using the high energy
physics package:
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<em>A represents only gamma5 in vector expressions</em>You have tried to use A i
n some way other than gamma5 in a
high-energy physics expression.
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<em>Gamma5 not allowed unless vecdim is 4</em>You have used gamma_5 in a high-en
ergy physics
computation involving a vector dimension other than 4.
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<ID> <em>has no mass</em>
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One of the arguments to
<A HREF=r37_0414.html>mshell</A> has had no mass assigned to it, in
high-energy physics calculations.
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<em>Missing arguments for G operator</em>A line symbol is missing in a gamma mat
rix expression in high-energy physics
calculations.
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<em>Unmatched index</em><list>
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The parser has found unmatched indices during the evaluation of a
gamma matrix expression in high-energy physics calculations.
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