(mu, lower=False)
return m
r"""Returns a Dirac gamma matrix `\gamma^\mu` in the standard
    (Dirac) representation.

    If you want `\gamma_\mu`, use ``gamma(mu, True)``.

    We use a convention:

    `\gamma^5 = i \cdot \gamma^0 \cdot \gamma^1 \cdot \gamma^2 \cdot \gamma^3`

    `\gamma_5 = i \cdot \gamma_0 \cdot \gamma_1 \cdot \gamma_2 \cdot \gamma_3 = - \gamma^5`

    References
    ==========

    .. [1] http://en.wikipedia.org/wiki/Gamma_matrices

    Examples
    ========

    >>> from sympy.physics.matrices import mgamma
    >>> mgamma(1)
    Matrix([
    [ 0,  0, 0, 1],
    [ 0,  0, 1, 0],
    [ 0, -1, 0, 0],
    [-1,  0, 0, 0]])
r"""Returns a Dirac gamma matrix `\gamma^\mu` in the standard
    (Dirac) representation.
r Returns a Dirac gamma matrix \ gamma^ \ mu in the standard ( Dirac ) representation .
def mgamma(mu, lower=False):
    r"""Returns a Dirac gamma matrix `\gamma^\mu` in the standard
    (Dirac) representation.

    If you want `\gamma_\mu`, use ``gamma(mu, True)``.

    We use a convention:

    `\gamma^5 = i \cdot \gamma^0 \cdot \gamma^1 \cdot \gamma^2 \cdot \gamma^3`

    `\gamma_5 = i \cdot \gamma_0 \cdot \gamma_1 \cdot \gamma_2 \cdot \gamma_3 = - \gamma^5`

    References
    ==========

    .. [1] http://en.wikipedia.org/wiki/Gamma_matrices

    Examples
    ========

    >>> from sympy.physics.matrices import mgamma
    >>> mgamma(1)
    Matrix([
    [ 0,  0, 0, 1],
    [ 0,  0, 1, 0],
    [ 0, -1, 0, 0],
    [-1,  0, 0, 0]])
    """
    if not mu in [0, 1, 2, 3, 5]:
        raise IndexError("Invalid Dirac index")
    if mu == 0:
        mat = (
            (1, 0, 0, 0),
            (0, 1, 0, 0),
            (0, 0, -1, 0),
            (0, 0, 0, -1)
        )
    elif mu == 1:
        mat = (
            (0, 0, 0, 1),
            (0, 0, 1, 0),
            (0, -1, 0, 0),
            (-1, 0, 0, 0)
        )
    elif mu == 2:
        mat = (
            (0, 0, 0, -I),
            (0, 0, I, 0),
            (0, I, 0, 0),
            (-I, 0, 0, 0)
        )
    elif mu == 3:
        mat = (
            (0, 0, 1, 0),
            (0, 0, 0, -1),
            (-1, 0, 0, 0),
            (0, 1, 0, 0)
        )
    elif mu == 5:
        mat = (
            (0, 0, 1, 0),
            (0, 0, 0, 1),
            (1, 0, 0, 0),
            (0, 1, 0, 0)
        )
    m = Matrix(mat)
    if lower:
        if mu in [1, 2, 3, 5]:
            m = -m
    return m
def mgamma ( mu , lower = False ) : if not mu in [ 0 , 1 , 2 , 3 , 5 ] : raise IndexError ( "Invalid Dirac index" ) if mu == 0 : mat = ( ( 1 , 0 , 0 , 0 ) , ( 0 , 1 , 0 , 0 ) , ( 0 , 0 , - 1 , 0 ) , ( 0 , 0 , 0 , - 1 ) ) elif mu == 1 : mat = ( ( 0 , 0 , 0 , 1 ) , ( 0 , 0 , 1 , 0 ) , ( 0 , - 1 , 0 , 0 ) , ( - 1 , 0 , 0 , 0 ) ) elif mu == 2 : mat = ( ( 0 , 0 , 0 , - I ) , ( 0 , 0 , I , 0 ) , ( 0 , I , 0 , 0 ) , ( - I , 0 , 0 , 0 ) ) elif mu == 3 : mat = ( ( 0 , 0 , 1 , 0 ) , ( 0 , 0 , 0 , - 1 ) , ( - 1 , 0 , 0 , 0 ) , ( 0 , 1 , 0 , 0 ) ) elif mu == 5 : mat = ( ( 0 , 0 , 1 , 0 ) , ( 0 , 0 , 0 , 1 ) , ( 1 , 0 , 0 , 0 ) , ( 0 , 1 , 0 , 0 ) ) m = Matrix ( mat ) if lower : if mu in [ 1 , 2 , 3 , 5 ] : m = - m return m