diff --git a/pyphare/pyphare/core/operators.py b/pyphare/pyphare/core/operators.py
index d9978d713..3afe3911d 100644
--- a/pyphare/pyphare/core/operators.py
+++ b/pyphare/pyphare/core/operators.py
@@ -3,7 +3,18 @@
 from pyphare.pharesee.hierarchy import ScalarField, VectorField#, TensorField
 
 
-# TODO commencer par calculer z=hier*hier puis racine caree du dataset
+def _compute_dot_product(patchdatas, **kwargs):
+
+    pd_attrs = []
+
+    return tuple(pd_attrs)
+
+
+def dot(hier_a, hier_b):
+
+    # doit utiliser un compute_hier_from
+
+    return hier_a
 
 
 def sqrt(hier):
@@ -48,59 +59,4 @@ def modulus(hier):
 
 
 
-def sqrt_old(hierarchy):
-
-    """
-    returns a Hierarchy of the same type of the input (which can be
-    ScalarField, VectorField or Tensor2Field) containing the square root
-    of each dataset
-
-    """
-
-    patch_levels = hierarchy.patch_levels
-    domain_box = hierarchy.domain_box
-
-    num_of_components = len(hierarchy.levels()[0].patches[0].patch_datas.keys())
-
-    if num_of_components == 1:
-        names = ['value']
-    elif num_of_components == 3:
-        names = ['x', 'y', 'z']
-    elif num_of_components == 6:
-        names = ['xx', 'xy', 'xz', 'yy', 'yz', 'zz']
-    elif num_of_components == 9:
-        names = ['xx', 'xy', 'xz', 'yx', 'yy', 'yz', 'zx', 'zy', 'zz']
-
-
-    for time in list(hierarchy.time_hier.keys()):
-        new_patch_level = {}
-
-        for ilvl, lvl in hierarchy.levels(time).items():
-            new_patches = {}
-
-            for patch in lvl.patches:
-                new_pd = {}
-                layout = patch.layout
-
-                num_of_components = len(patch.patch_datas.keys())
-
-                for (name, pd_name) in zip(names, patch.patch_datas.keys()):
-                    dset = np.sqrt(np.asarray(patch.patch_datas[pd_name].dataset))
-
-                    pd = FieldData(layout, name, dset, centering=patch.patch_datas[pd_name].centerings)
-                    new_pd[name] = pd
-
-                if ilvl not in new_patches:
-                    new_patches[ilvl] = []
-
-                new_patches[ilvl].append(Patch(new_pd, patch.id))
-
-            new_patch_level[ilvl] = PatchLevel(ilvl, new_patches[ilvl])
-
-    if num_of_components == 1:
-        return ScalarField(new_patch_level, domain_box, time=time)
-    if num_of_components == 3:
-        return VectorField(new_patch_level, domain_box, time=time)
-    if num_of_components == 6 or num_of_components == 9:
-        return Tensor2Field(new_patch_level, domain_box, time=time)
 
diff --git a/pyphare/pyphare/pharesee/hierarchy.py b/pyphare/pyphare/pharesee/hierarchy.py
index cc3ea232e..c4728e3ce 100644
--- a/pyphare/pyphare/pharesee/hierarchy.py
+++ b/pyphare/pyphare/pharesee/hierarchy.py
@@ -1093,7 +1093,7 @@ def __init__(self, patch_levels, domain_box, **kwargs):
         time = kwargs.get("time", .0)
         data_files = kwargs.get("data_files", None)
 
-        self.name = ['scalar'] # TODO should we use the static name ?
+        # self.name = ['scalar'] # TODO should we use the static name ?
 
         super().__init__(patch_levels, domain_box, refinement_ratio, time, data_files)