From 6ebff8cedf852bcb77c5ff14791b7fc1c18695e7 Mon Sep 17 00:00:00 2001
From: mcditooss <gerardofingurbe@gmail.com>
Date: Tue, 8 Oct 2024 16:38:21 +0200
Subject: [PATCH] Remove T=0 related error

---
 qutip/core/environment.py | 6 +++++-
 qutip/utilities.py        | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/qutip/core/environment.py b/qutip/core/environment.py
index e3e4414082..c0e9fbd5aa 100644
--- a/qutip/core/environment.py
+++ b/qutip/core/environment.py
@@ -1186,7 +1186,10 @@ def approx_by_matsubara(
 
     def _matsubara_params(self, Nk):
         """ Calculate the Matsubara coefficients and frequencies. """
-        beta = 1 / self.T
+        if self.T==0:
+            beta=np.Inf
+        else:    
+            beta = 1 / self.T
         Om = np.sqrt(self.w0**2 - (self.gamma / 2)**2)
         Gamma = self.gamma / 2
 
@@ -1624,6 +1627,7 @@ def __init__(
             exponents = self.combine(exponents)
         self.exponents = exponents
 
+
     @classmethod
     def combine(
         cls, exponents: Sequence[CFExponent],
diff --git a/qutip/utilities.py b/qutip/utilities.py
index ba143f0765..143a4c7a51 100644
--- a/qutip/utilities.py
+++ b/qutip/utilities.py
@@ -471,7 +471,7 @@ def _rmse(fun, xdata, ydata, params):
     parameters. (The closer to zero = the better the fit.)
     """
     yhat = _evaluate(fun, xdata, params)
-    if (np.max(ydata) - np.min(ydata)) == 0.0:
+    if (yhat == ydata).all():
         return 0
     return (
         np.sqrt(np.mean((yhat - ydata) ** 2) / len(ydata))