My form with Ajax does not work (is not valid). Why?

Concursos.php

<?php
namespace Admin\Entity;

use DateTime;
use Doctrine\ORM\Mapping as ORM;

/**
* @ORM\Entity
* @ORM\Table(name="concursos")
*/
class Concursos
{
	/**
	* @ORM\Id
	* @ORM\Column(name="id", type="integer")
	* @ORM\GeneratedValue(strategy="AUTO")
	*/
	protected $id;

	/** @ORM\Column(name="titulo", type="string", length=150, nullable=false) */
	protected $titulo;

    /** @ORM\Column(name="fecha", type="date", nullable=false) */
    protected $fecha;

    /** @ORM\Column(name="cuerpo", type="string", nullable=false) */
    protected $cuerpo;

    public function getId() {
    	return $this->id;
    }

    public function setTitulo($titulo) {
        $this->titulo = $titulo;
    }

    public function getTitulo() {
        return $this->titulo;
    }

    public function setFecha(DateTime $fecha) {
        $this->fecha = $fecha;
    }

    public function getFecha() {
        return $this->fecha;
    }

    public function setCuerpo($cuerpo) {
        $this->cuerpo = $cuerpo;
    }

    public function getCuerpo() {
        return $this->cuerpo;
    }
}

ConcursosController.php

<?php
namespace Admin\Controller;

use Zend\Mvc\Controller\AbstractActionController;
use DoctrineORMModule\Paginator\Adapter\DoctrinePaginator;
use Doctrine\ORM\Tools\Pagination\Paginator as ORMPaginator;
use Zend\Paginator\Paginator;
use Zend\View\Model\ViewModel;

class ConcursosController extends AbstractActionController
{
	/**
	* @var Doctrine\ORM\EntityManager
	*/
	protected $em;
	 
	public function getEntityManager()
	{
		if(null === $this->em)
			$this->em = $this->getServiceLocator()->get('doctrine.entitymanager.orm_default');
			return $this->em;
	}
    public function crearAction()
    {
        $objectManager = $this->getServiceLocator()->get('Doctrine\ORM\EntityManager');
        $form = new \Admin\Form\ConcursosForm($objectManager);
        $concurso = new \Admin\Entity\Concursos();
        $form->bind($concurso);

        $viewmodel = new ViewModel();
        $viewmodel->setTerminal($this->getRequest()->isXmlHttpRequest());
        $viewmodel->setVariables(array('form' => $form));

        if($this->getRequest()->isXmlHttpRequest()){
            $form->setData($this->getRequest()->getPost());
            if($form->isValid()){
                $objectManager->persist($concurso);
                $objectManager->flush();
            }
        }

        return $viewmodel;
    }
    public function guardarAction()
    {
        $objectManager = $this->getServiceLocator()->get('Doctrine\ORM\EntityManager');

        $form = new \Admin\Form\ConcursosForm($objectManager);
        $concurso = new \Admin\Entity\Concursos();
        $form->bind($concurso);

        if($this->getRequest()->isXmlHttpRequest()){
            if($this->getRequest()->isPost()){
                $form->setData($this->getRequest()->getPost());
                $hello = 0;
                if($form->isValid()){
                    $hello = 1;
                    $objectManager->persist($concurso);
                    $objectManager->flush();
                }else{
                    foreach($form->getMessages() as $key=>$row)
                        if(!empty($row) && $key != 'submit')
                            foreach($row as $keyer => $rower)
                                $messages[$key][] = $rower;
                }
                if(!empty($messages))
                    $this->getResponse()->setContent(\Zend\Json\Json::encode($messages));
                else
                    $this->getResponse()->setContent(\Zend\Json\Json::encode(array('hello' => $hello)));
            }
            return $this->getResponse();
        }
    }
}

ConcursosFieldset.php

<?php
namespace Admin\Form;

use Admin\Entity\Concursos;
use Doctrine\Common\Persistence\ObjectManager;
use DoctrineModule\Stdlib\Hydrator\DoctrineObject as DoctrineHydrator;
use Zend\Form\Fieldset;
use Zend\InputFilter\InputFilterProviderInterface;

class ConcursosFieldset extends Fieldset implements InputFilterProviderInterface
{
    public function __construct(ObjectManager $objectManager)
    {
        parent::__construct('concursos');

        $this->setHydrator(new DoctrineHydrator($objectManager,'Admin\Entity\Concursos'))
             ->setObject(new Concursos());

        $this->add(array(
            'name' => 'titulo',
            'type' => 'Zend\Form\Element\Text',
            'attributes' => array(
                'required'      => 'required',
                'placeholder'   => 'Ingrese aquí un título',
                'class'         => 'form-control titulo',
                'autocomplete'  => 'off'
            ),
        ));

        $this->add(array(
            'name' => 'fecha',
            'type' => 'Zend\Form\Element\Text',
            'attributes' => array(
                'id'            => 'fecha',
                'placeholder'   => '31/01/2016',
                'class'         => 'form-control fecha',
                'autocomplete'  => 'off'
            ),
        ));

        $this->add(array(
            'name' => 'cuerpo',
            'type' => 'Zend\Form\Element\Textarea',
            'attributes' => array(
                'required'      => 'required',
                'placeholder'   => 'Ingrese aquí un cuerpo',
                'class'         => 'form-control cuerpo',
                'autocomplete'  => 'off'
            ),
        ));
    }

    public function getInputFilterSpecification()
    {
        return array(
            'titulo' => array(
                'required' => true,
            ),
            'fecha' => array(
                'required' => true,
            ),
            'cuerpo' => array(
                'required' => true,
            ),
        );
    }
}

ConcursosForm.php

<?php
namespace Admin\Form;

use Doctrine\Common\Persistence\ObjectManager;
use DoctrineModule\Stdlib\Hydrator\DoctrineObject as DoctrineHydrator;
use Zend\Form\Form;

class ConcursosForm extends Form
{
    public function __construct(ObjectManager $objectManager)
    {
        parent::__construct('concursos');

        $this->setHydrator(new DoctrineHydrator($objectManager,'Admin\Entity\Concursos'))->setObject(new \Admin\Entity\Concursos());

        $concurso = new \Admin\Form\ConcursosFieldset($objectManager);
        $concurso->setName('concurso');
        $concurso->setUseAsBaseFieldset(true);
        $this->add($concurso);

        $this->add(array(
            'type' => 'Zend\Form\Element\Csrf',
            'name' => 'csrf',
        ));

        $this->add(array(
            'name' => 'submit',
            'attributes' => array(
                'class' => 'form-control btn btn-primary',
                'type'  => 'submit',
                'value' => 'Publicar concurso',
            ),
        ));
        /*$this->setValidationGroup(array(
            'csrf',
            'concurso' => array(
                'titulo',
                'fecha',
                'cuerpo'
            )
        ));*/
    }
}

crear.phtml

<?php
$this->headLink()
     ->prependStylesheet($this->basePath().'/js/jquery-ui/jquery-ui.min.css');
$this->headScript()
     ->appendFile($this->basePath().'/js/jquery-ui/jquery-ui.min.js')
     ->appendFile($this->basePath().'/js/ajax/ajax-dialog.js');
?>
<?php
//$form->setAttribute('action', $this->url('concursos/default', array('action' => 'guardar')))->prepare();
echo $this->form()->openTag($form);
$concurso = $form->get('concurso');
?>

<br>
<?php echo $this->formRow($concurso->get('titulo')); ?>

<br>
<script> $(function() { $('#fecha').datepicker({dateFormat: 'yy-mm-dd'}); }); </script>
<div class="expiro">
    <label>Fecha de expiro: </label>
    <?php echo $this->formRow($concurso->get('fecha')); ?>
</div>

<br>
<div class="cuerpo">
    <?php echo $this->formRow($concurso->get('cuerpo')); ?>
</div>

<br>
<?php echo $this->formRow($form->get('csrf')); ?>

<?php echo $this->formRow($form->get('submit')); ?>

<?php echo $this->form()->closeTag(); ?>

<a id="hola">x</a>
<div id="xxx"></div>
<script>
//$('#concursos').submit(function(){
$('#hola').click(function(){
    $.ajax({
        url: "<?php echo $this->url('concursos/default', array('action' => 'crear')); ?>",
        type: 'POST',
        dataType: 'json',
        contentType: "application/json; charset=utf-8",
        async: true,
        data: $('#concursos').serialize(),
        success: function (data) {
            alert('No hay error, y España te ataca.');
            $("#xxx").html(data);
            console.log('Enviando información..');
            console.log(data);
        },
        error: function (data) {
            //alert('Error al enviar la información..');
            console.log('Error al enviar la información..');
        }
    });
});
</script>