<?= GridView::widget([
                'dataProvider' => $dataProvider,
                'columns' => [
                    ['class' => 'yii\grid\SerialColumn'],
                    'title',
                    'author' => [
                        'class' => \yii\grid\DataColumn::className(),
                        'format' => 'html',
                        'value' => function ($model, $index, $widget) {
                            return $model->author->name ;
                        },
                    ],
                   // и т.п. ...

public function getAuthor() {
        return $this->hasOne(Authors::className(), ['id' => 'author_id']);
    }