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.
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
- One or more equations did not get rendered due to their size.
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.
A sum of extended nonnegative reals which is finite can have only finitely many terms above any positive threshold.
Markov's inequality for Finset.card
and tsum
in ℝ≥0∞
.
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
.
If a sequence f
with non-negative terms is dominated by a sequence g
with summable
series and at least one term of f
is strictly smaller than the corresponding term in g
,
then the series of f
is strictly smaller than the series of g
.
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.
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 ≠ ∞
.
Equations
- ENNReal.truncateToReal t x = (min t x).toReal
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)
.