Topology on extended non-negative reals #
Topology on ℝ≥0∞
.
Note: this is different from the EMetricSpace
topology. The EMetricSpace
topology has
IsOpen {∞}
, while this topology doesn't have singleton elements.
Equations
The set of finite ℝ≥0∞
numbers is homeomorphic to ℝ≥0
.
Equations
- ENNReal.neTopHomeomorphNNReal = { toEquiv := ENNReal.neTopEquivNNReal, continuous_toFun := ENNReal.neTopHomeomorphNNReal.proof_1, continuous_invFun := ENNReal.neTopHomeomorphNNReal.proof_2 }
Instances For
The set of finite ℝ≥0∞
numbers is homeomorphic to ℝ≥0
.
Equations
Instances For
Characterization of neighborhoods for ℝ≥0∞
numbers. See also tendsto_order
for a version with strict inequalities.
Equations
Equations
The sum over the complement of a finset tends to 0
when the finset grows to cover the whole
space. This does not need a summability assumption, as otherwise all sums are zero.
Summable non-negative functions have countable support
A series of non-negative real numbers converges to r
in the sense of HasSum
if and only if
the sequence of partial sum converges to r
.
For f : ℕ → ℝ≥0
, then ∑' k, f (k + i)
tends to zero. This does not require a summability
assumption on f
, as otherwise all sums are zero.
Finitely summable non-negative functions have countable support
A series of non-negative real numbers converges to r
in the sense of HasSum
if and only if
the sequence of partial sum converges to r
.
In an emetric ball, the distance between points is everywhere finite
Each ball in an extended metric space gives us a metric space, as the edist is everywhere finite.
Equations
Instances For
Yet another metric characterization of Cauchy sequences on integers. This one is often the most efficient.
If the extended distance between consecutive points of a sequence is estimated
by a summable series of NNReal
s, then the original sequence is a Cauchy sequence.
For a bounded set s : Set ℝ
, its EMetric.diam
is equal to sSup s - sInf s
reinterpreted as
ℝ≥0∞
.
For a bounded set s : Set ℝ
, its Metric.diam
is equal to sSup s - sInf s
.
If edist (f n) (f (n+1))
is bounded above by a function d : ℕ → ℝ≥0∞
,
then the distance from f n
to the limit is bounded by ∑'_{k=n}^∞ d k
.
If edist (f n) (f (n+1))
is bounded above by a function d : ℕ → ℝ≥0∞
,
then the distance from f 0
to the limit is bounded by ∑'_{k=0}^∞ d k
.
With truncation level t
, the truncated cast ℝ≥0∞ → ℝ
is given by x ↦ (min t x).toReal
.
Unlike ENNReal.toReal
, this cast is continuous and monotone when t ≠ ∞
.
Instances For
The truncated cast ENNReal.truncateToReal t : ℝ≥0∞ → ℝ
is monotone when t ≠ ∞
.
The truncated cast ENNReal.truncateToReal t : ℝ≥0∞ → ℝ
is continuous when t ≠ ∞
.
If xs : ι → ℝ≥0∞
is bounded, then we have liminf (toReal ∘ xs) = toReal (liminf xs)
.
If xs : ι → ℝ≥0∞
is bounded, then we have liminf (toReal ∘ xs) = toReal (liminf xs)
.