Tuning knob param for 1-halo 2-point correlations (#883)

* Profile2ptR - to be amended

* implemented r_corr in Profile2pt

pyccl/halos/profiles_2pt.py

@@ -2,38 +2,63 @@
 
 
 class Profile2pt(object):
-    """ This class implements the 1-halo 2-point correlator between two
-    halo profiles. In the simplest case, this is just
-    the product of both profiles in Fourier space.
-    More complicated cases should be implemented by subclassing
-    this class and overloading the :meth:`~Profile2pt.fourier_2pt`
-    method.
+    """ This class implements the 1-halo 2-point correlator between
+    two halo profiles.
+
+    .. math::
+        \\langle u_1(k) u_2(k) \\rangle.
+
+    In the simplest case the second-order cumulant is just the product
+    of the individual Fourier-space profiles. More complicated cases
+    are implemented via the parameters of this class.
+
+    Args:
+        r_corr (float):
+            Tuning knob for the 1-halo 2-point correlation.
+            Scale the correlation by :math:`(1+\\rho_{u_1, u_2})`.
+            This is useful when the individual 1-halo terms
+            are not fully correlated. Example usecases can be found
+            in ``arXiv:1909.09102`` and ``arXiv:2102.07701``.
+            Defaults to ``r_corr=0``, returning simply the product
+            of the fourier profiles.
+
     """
-    def __init__(self):
-        pass
+    def __init__(self, r_corr=0.):
+        self.r_corr = r_corr
+
+    def update_parameters(self, r_corr=None):
+        """ Update any of the parameters associated with this 1-halo
+        2-point correlator. Any parameter set to `None` won't be updated.
+        """
+        if r_corr is not None:
+            self.r_corr = r_corr
 
     def fourier_2pt(self, prof, cosmo, k, M, a,
                     prof2=None, mass_def=None):
-        """ Returns the Fourier-space two-point moment between
-        two profiles:
+        """ Return the Fourier-space two-point moment between
+        two profiles.
 
         .. math::
-           \\langle\\rho_1(k)\\rho_2(k)\\rangle.
+           (1+\\rho_{u_1,u_2})\\langle u_1(k)\\rangle\\langle u_2(k) \\rangle
 
         Args:
             prof (:class:`~pyccl.halos.profiles.HaloProfile`):
                 halo profile for which the second-order moment
                 is desired.
-            cosmo (:class:`~pyccl.core.Cosmology`): a Cosmology object.
-            k (float or array_like): comoving wavenumber in Mpc^-1.
-            M (float or array_like): halo mass in units of M_sun.
-            a (float): scale factor.
+            cosmo (:class:`~pyccl.core.Cosmology`):
+                a Cosmology object.
+            k (float or array_like):
+                comoving wavenumber in Mpc^-1.
+            M (float or array_like):
+                halo mass in units of M_sun.
+            a (float):
+                scale factor.
             prof2 (:class:`~pyccl.halos.profiles.HaloProfile`):
                 second halo profile for which the second-order moment
                 is desired. If `None`, the assumption is that you want
                 an auto-correlation, and `prof` will be used as `prof2`.
-            mass_def (:obj:`~pyccl.halos.massdef.MassDef`): a mass
-                definition object.
+            mass_def (:obj:`~pyccl.halos.massdef.MassDef`):
+                a mass definition object.
 
         Returns:
             float or array_like: second-order Fourier-space
@@ -44,6 +69,7 @@ def fourier_2pt(self, prof, cosmo, k, M, a,
         """
         if not isinstance(prof, HaloProfile):
             raise TypeError("prof must be of type `HaloProfile`")
+
         uk1 = prof.fourier(cosmo, k, M, a, mass_def=mass_def)
 
         if prof2 is None:
@@ -55,7 +81,7 @@ def fourier_2pt(self, prof, cosmo, k, M, a,
 
             uk2 = prof2.fourier(cosmo, k, M, a, mass_def=mass_def)
 
-        return uk1 * uk2
+        return uk1 * uk2 * (1 + self.r_corr)
 
 
 class Profile2ptHOD(Profile2pt):

pyccl/tests/test_profiles.py

@@ -174,6 +174,29 @@ def test_hod_2pt_raises():
                    prof2=pgood, mass_def=M200)
 
 
+def test_2pt_rcorr_smoke():
+    c = ccl.halos.ConcentrationDuffy08(M200)
+    p = ccl.halos.HaloProfileNFW(c_M_relation=c)
+    F0 = ccl.halos.Profile2pt().fourier_2pt(p, COSMO, 1., 1e13, 1.,
+                                            mass_def=M200)
+    p2pt = ccl.halos.Profile2pt(r_corr=0)
+    F1 = p2pt.fourier_2pt(p, COSMO, 1., 1e13, 1., mass_def=M200)
+    assert F0 == F1
+    F2 = p2pt.fourier_2pt(p, COSMO, 1., 1e13, 1., prof2=p, mass_def=M200)
+    assert F1 == F2
+
+    p2pt.update_parameters(r_corr=-1.)
+    assert p2pt.r_corr == -1.
+    F3 = p2pt.fourier_2pt(p, COSMO, 1., 1e13, 1., mass_def=M200)
+    assert F3 == 0
+
+    # Errors
+    with pytest.raises(TypeError):
+        p2pt.fourier_2pt(None, COSMO, 1., 1e13, 1., mass_def=M200)
+    with pytest.raises(TypeError):
+        p2pt.fourier_2pt(p, COSMO, 1., 1e13, 1., prof2=0, mass_def=M200)
+
+
 @pytest.mark.parametrize('prof_class',
                          [ccl.halos.HaloProfileGaussian,
                           ccl.halos.HaloProfilePowerLaw])