Errors with elsarticle document class

Question

I'm using the elsarticle document class on ShareLaTeX, and it is giving five errors that don't make much sense to me.

My code is

\documentclass{elsarticle}
\usepackage{pifont, natbib, geometry, fleqn, graphicx, txfonts,hyperref}
\usepackage{amssymb,amsmath,parskip}

\title{plasma paper}
\author{Garrett Young}

\begin{document}

\maketitle

\section{Introduction}
Lorentz force equations:
\begin{equation}
    \mathbf{F} = \mathbf{-\mathit{e}(E + v \times B)} = m\frac{d\mathbf{v}}{dt}
\end{equation}
\end{document}

And the errors are

/usr/local/texlive/2015/texmf-dist/tex/latex/amsmath/amsmath.sty, line 505
LaTeX Error: Command \iint already defined.
Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.505 ...d{\iint}{\DOTSI\protect\MultiIntegral{2}}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.
 /usr/local/texlive/2015/texmf-dist/tex/latex/amsmath/amsmath.sty, line 506
LaTeX Error: Command \iiint already defined.
Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.506 ...{\iiint}{\DOTSI\protect\MultiIntegral{3}}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.
 /usr/local/texlive/2015/texmf-dist/tex/latex/amsmath/amsmath.sty, line 507
LaTeX Error: Command \iiiint already defined.
Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.507 ...\iiiint}{\DOTSI\protect\MultiIntegral{4}}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.
 /usr/local/texlive/2015/texmf-dist/tex/latex/amsmath/amsmath.sty, line 508
LaTeX Error: Command \idotsint already defined.
Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.508 ...dotsint}{\DOTSI\protect\MultiIntegral{0}}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.
 /usr/local/texlive/2015/texmf-dist/tex/latex/base/fleqn.sty
inputting `fleqn.clo' instead of obsolete `fleqn.sty'.

The content shows up correctly. I don't really know what's wrong. Any help would be appreciated.

Answer 1

There are a number of symbols defined inside txfonts that are also defined in amsmath, so you can just make these available again:

\usepackage{txfonts}
\let\iint\relax
\let\iiint\relax
\let\iiiint\relax
\let\idotsint\relax
\usepackage{amsmath}

However, the following is better:

\documentclass{elsarticle}

\usepackage{newtxtext,newtxmath}
\usepackage{amsmath}

\begin{document}

Lorem ipsum \ldots

\end{document}

From the newtx README:

The bun­dle splits tx­fonts.sty (from the TX fonts dis­tri­bu­tion) into two in­de­pen­dent pack­ages, newtx­text.sty and newtx­math.sty, each with fixes and enhancements.

It seems like the fixes might include the symbol definitions being removed.