Help using google maps api

Help using google maps api

Hi, I'm developping a mobile application, and I've got a problem displaying a map, even if it seems to be really easy.
Here's my HTML page :

<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
  <style type="text/css">
    html { height: 100% }
    body { height: 100%; margin: 0px; padding: 0px }
    #map_canvas { height: 100% ; width:100%;}
  </style>
  <script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false"></script> 
</head>
<body>
  <div id="map_canvas"></div>
</body>

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7/jquery.min.js" type="text/javascript"></script>
<script src="jquery-ui-map-3.0-rc/ui/min/jquery.ui.map.full.min.js" type="text/javascript"></script>
<script src="jquery.mobile-1.4.2/demos/js/jquery.js"></script>
<script src="jquery.mobile-1.4.2/jquery.mobile-1.4.2.min.js"></script>
<script type="text/javascript" src="js/index.js"></script>
<script type="text/javascript">
    app.initialize();
</script>

<script type="text/javascript">
  $(function() {
                // Also works with: var yourStartLatLng = '59.3426606750, 18.0736160278';
                var yourStartLatLng = new google.maps.LatLng(59.3426606750, 18.0736160278);
                $('#map_canvas').gmap({'center': yourStartLatLng});
  });   
</script>
</html>

When I load it I've got nothing, and the console log tell me "Uncaught TypeError: undefined is not a function" at the line " $('#map_canvas').gmap({'center': yourStartLatLng});"
I just picked up this code on a tutorial and I added some javascript that I need, maybe I'm an idiot but I spent all the morning on it, now I need your help !

Thank you :)