Fixed wrong mean in Field.power_synthesize.

nifty/field.py

@@ -287,6 +287,10 @@ class Field(Loggable, Versionable, object):
 
     def power_synthesize(self, spaces=None, real_signal=True,
                          mean=None, std=None):
+
+        if mean is None:
+            mean = 1.
+
         # assert that all spaces in `self.domain` are either of signal-type or
         # power_space instances
         for sp in self.domain:

nifty/sugar.py

@@ -20,7 +20,7 @@ def create_power_operator(domain, power_spectrum, distribution_strategy='not'):
                val=power_spectrum,
                distribution_strategy=distribution_strategy)
 
-    f = fp.power_synthesize(mean=1, std=0)
+    f = fp.power_synthesize(std=0)
 
     power_operator = DiagonalOperator(domain, diagonal=f)