$p$-adic measures associated with zeta values and $p$-adic $\log$ multiple gamma functions
Tomokazu Kashio

TL;DR
This paper explores the relationship between two $p$-adic symbols related to Gross-Stark units, connecting $p$-adic gamma functions and multiplicative integration to deepen understanding of $p$-adic $L$-values and units.
Contribution
It establishes an explicit relation between Yoshida's $Y_p( au)$ symbol and Dasgupta's $u_T( au)$ symbol, linking two approaches to Gross-Stark units.
Findings
Derived an explicit formula relating $Y_p( au)$ and $u_T( au)$
Connected $p$-adic gamma functions with multiplicative integration methods
Enhanced understanding of $p$-adic units in abelian extensions
Abstract
We study a relation between two refinements of the rank one abelian Gross-Stark conjecture: For a suitable abelian extension of number fields, a Gross-Stark unit is defined as a -unit of satisfying some proporties. Let . Yoshida and the author constructed the symbol by using -adic multiple gamma functions, and conjectured that the of a Gross-Stark unit can be expressed by . Dasgupta constructed the symbol by using the -adic multiplicative integration, and conjectured that a Gross-Stark unit can be expressed by . In this paper, we give an explicit relation between and .
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-adic measures associated with zeta values and -adic multiple gamma functions
Tomokazu Kashio Tokyo University of Science, [email protected]
Abstract
We study a relation between two refinements of the rank one abelian Gross-Stark conjecture: For a suitable abelian extension of number fields, a Gross-Stark unit is defined as a -unit of satisfying some proporties. Let . Yoshida and the author constructed the symbol by using -adic multiple gamma functions, and conjectured that the of a Gross-Stark unit can be expressed by . Dasgupta constructed the symbol by using the -adic multiplicative integration, and conjectured that a Gross-Stark unit can be expressed by . In this paper, we give an explicit relation between and .
1 Introduction
Let be a totally real field, a CM-field which is abelian over , a finite set of places of . We assume that
- •
contains all infinite places of , all places of lying above a rational prime , and all ramified places in .
- •
Let be the prime ideal corresponding to the -adic topology on . (Hence .) Then splits completely in .
For , we consider the partial zeta function
[TABLE]
Here runs over all integral ideals of , relatively prime to any finite places in , whose image under the Artin symbol is equal to . The series converges for , has a meromorphic continuation to the whole -plane, and is analytic at . Moreover, under our assumption, we see that
- •
There exists the -adic interpolation function of .
- •
.
- •
There exist a natural number , a -unit of , which satisfy
[TABLE]
Here denotes the prime ideal corresponding to the -adic topology on , .
Gross conjectured the following -adic analogue of the rank abelian Stark conjecture:
Conjecture 1** ([Gr, Conjecture 3.13]).**
Let be a -unit characterized by (1) up to roots of unity. Then we have
[TABLE]
Dasgupta-Darmon-Pollack [DDP] proved a large part of Conjecture 1. Yoshida and the author, and independently Dasgupta formulated refinements of Conjecture 1: Let be an integral ideal of a totally real field satisfying , the narrow ray class field modulo , the maximal subfield of where splits completely. Yoshida and the author [KY1] essentially constructed the invariant (Definition 6) for by using -adic multiple gamma functions. Then [KY1, Conjecture A*′*] states that (without ) can be expressed by . On the other hand, Dasgupta constructed the invariant (Definition 12-(iv)) by using the multiplicative integration for -adic measures associated with Shintani’s multiple zeta functions. Then [Da, Conjecture 3.21] states that a modified version of can be expressed by . In [Ka3, Remark 2], the author announced the following relation between these refinements.
Theorem** (Theorem 1).**
Let be a “good” prime ideal in the sense of Definition 11. We put . Then we have
[TABLE]
In particular, we see that two refinements are consistent (roughly speaking, [Da, Conjecture 3.21] is a further refinement of [KY1, Conjecture A*′*] by ). The aim of this paper is to prove this Theorem.
Let us explain the outline of this paper. In §2, we introduce Shintani’s technique of cone decompositions. We obtain a suitable fundamental domain of , where denotes the totally positive part of , is a subgroup of the group of all totally positive units. We need such fundamental domains in order to construct both of the invariants , . In §3, we recall the definition and some properties of , which is essentially defined in [KY1] and slightly modified in [Ka3]. The classical or -adic multiple gamma function is defined as the derivative values at of the classical or -adic Barnes’ multiple zeta function, respectively. Then the invariant is defined in Definition 6, as a finite sum of the “difference” of -adic multiple gamma functions and classical multiple gamma functions. Conjecture 2 predicts exact values of . In §4, we also recall some results in [Da]. Dasgupta introduced -adic measures associated with special values of Shintani’s multiple zeta functions, and defined as the multiplicative integration with certain correction terms. Dasgupta formulated a conjecture (Conjecture 3) on properties of . In §5, we state and prove the main result (Theorem 1) which gives an explicit relation between and . Then we will see that Conjectures 2, 3 are consistent in the sense of Corollary 1. The key observation is Lemma 3: Dasgupta’s -adic measure is originally associated with Shintani’s multiple zeta functions. By this Lemma, we can relate to Barnes’ multiple zeta functions and -adic analogues as in Lemma 4.
2 Shintani domains
Let be a totally real field of degree , the ring of integers of , an integral ideal of . We denote by the set of all totally positive elements in and put , . We consider subgroups of of the following form:
[TABLE]
We identify
[TABLE]
where denotes the set of all real embeddings of . In particular, the totally positive part
[TABLE]
has a meaning. On the right-hand side, denotes the set of all positive real numbers. Let be linearly independent. Then we define the cone with basis as
[TABLE]
Here we denotes the inner product.
Definition 1**.**
- (i)
We call a subset is a Shintani set if it can be expressed as a finite disjoint union of cones:
[TABLE] 2. (ii)
We consider the natural action , . We call a Shintani set a Shintani domain if it is a fundamental domain of :
[TABLE]
When , we write instead of .
Shintani [Sh, Proposition 4] showed that there always exists a Shintani domain.
3 -adic multiple gamma functions
We recall the definition and some properties of the symbol defined in [KY1], [Ka3]. We denote by the set of all positive real numbers.
Definition 2**.**
Let , . Barnes’ multiple zeta function is defined as
[TABLE]
This series converges for , has a meromorphic continuation to the whole -plane, and is analytic at . Then Barnes’ multiple gamma function is defined as
[TABLE]
Note that this definition is modified from that given by Barnes. For the proof and details, see [Yo, Chap I, §1]. Throughout this paper, we regard each number field as a subfield of , and fix two embeddings , . Here denotes the -adic completion of the algebraic closure of . We denote by the group of all roots of unity of prime-to- order. Let , be unique group homomorphisms satisfying
[TABLE]
Definition 3**.**
Let , . We assume that
[TABLE]
Then we denote by the -adic multiple zeta function characterized by
[TABLE]
We define the -adic multiple gamma function as
[TABLE]
The construction of is due to Cassou-Noguès [CN1]. The author defined and studied in [Ka1]. See [Ka3, §2] for a short survey.
Definition 4**.**
Let be a totally real field, an integral ideal, a Shintani domain . We denote by (resp. ) the set of all embeddings of into (resp. ). Since we fixed embeddings , , we may identify
[TABLE]
- (i)
We denote by the narrow ideal class group modulo , by the narrow ray class field modulo . In particular, the Artin map induces
[TABLE] 2. (ii)
Let be the natural projection. For each , we take an integral ideal satisfying
[TABLE] 3. (iii)
For , , we put
[TABLE] 4. (iv)
For , , we define
[TABLE] 5. (v)
For , we put
[TABLE]
Note that the prime ideal corresponds to the -adic topology on . 6. (vi)
Assume that . For , , we define
[TABLE]
Note that satisfies the assumption (3) whenever , .
The following map is well-defined by [KY1, Lemma 5.1].
Definition 5**.**
We denote by (resp. ) the -subspace of (resp. ) generated by (resp. , ) with . We define a -linear map by
[TABLE]
Lemma 1**.**
Let be an intermediate field of , a prime ideal of , relatively prime to , splitting completely in . Then we have
[TABLE]
Here runs over all ideal classes whose images under the composite map is equal to .
Proof.
We put in [KY1, (4.3)], in [KY1, (1.6)], and . Here we consider the ideal class group of modulo . Then denotes the image of in under the natural map. By the definition [KY1, (4.3)] and [KY2, Appendix I, Theorem], we have . Moreover [KY1, Lemma 5.5] states that
[TABLE]
Here , denote the composite map , the ideal class of , respectively. Therefore, when is the fixed subfield under , it follows from the orthogonality of characters. The general case follows from this case immediately. ∎
Definition 6**.**
Let be an intermediate field of . Assume that and that splits completely in . Then we define
[TABLE]
When , we drop the symbol : .
By [KY1, Proposition 5.6] (and the orthogonality of characters), we see that depends only on , not on , ’s. We formulated a conjecture [KY1, Conjecture A*′*], which is equivalent to the following Conjecture 2 by [Ka3, Proposition 6-(ii)].
Conjecture 2**.**
Let be as above: we assume that
* does not divide , splits completely in .*
We take a lift of and put . Let be a generator of the principal ideal , where denotes the class number. Then we have
[TABLE]
Remark 1**.**
Roughly speaking, the above conjecture states a relation between the ratios -adic multiple gamma functions multiple gamma functions and Stark units associated with the finite place . We also studied a relation between the same ratios and Stark units associated with real places in [Ka3]. We found a more significant relation between the ratios -adic gamma function gamma function and cyclotomic units in [Ka2].
We rewrite the definition of for later use.
Definition 7**.**
Let be a subset of . We assume that can be expressed in the following form:
[TABLE]
- (i)
We define
[TABLE] 2. (ii)
Additionally we assume that each satisfies (3). Then there exists the -adic interpolation function
[TABLE]
of . We define
[TABLE]
When , we drop the symbol .
It follows that, for any Shintani domain and for any integral ideals satisfying , we have
[TABLE]
where we put . We will use the following properties of the classical or -adic multiple gamma functions in the proof of Theorem 1.
Proposition 1**.**
- (i)
Let be as in Definition 7-(i), . Then we have
[TABLE] 2. (ii)
Let be as in Definition 7-(ii), . Then we have
[TABLE]
Proof.
The assertions follow from immediately. ∎
We also recall Shintani’s multiple zeta functions in [Sh, (1.1)] which we need in subsequent sections.
Definition 8**.**
- (i)
Let be an -matrix with , , with . Then Shintani’s multiple zeta function is defined as
[TABLE]
This series converges for , has a meromorphic continuation to the whole -plane, is analytic at . 2. (ii)
Let , be as in (i). For , we consider two kinds of Shintani’s multiple zeta functions:
- (a)
Shintani’s multiple zeta function with :
[TABLE]
Here we consider . 2. (b)
Let be the -matrix whose raw vectors are . Then we put
[TABLE] 3. (iii)
Let be as in Definition 7-(i). We define
[TABLE]
4 -adic measures associated with zeta values
We consider the following two kinds of integration.
Definition 9**.**
Let be a finite extension of , the ring of integers of , the maximal ideal of .
- (i)
We say is a -adic measure on if for each open compact subset , it takes the value satisfying
- (a)
* for disjoint open compact subsets .* 2. (b)
’s are bounded.
We say a -adic measure is a -valued measure if . 2. (ii)
Let be a -adic measure, a continuous map. We define
[TABLE] 3. (iii)
Let be a -valued measure, a continuous map . We define
[TABLE]
We recall the setting in [Da]. Let be a totally real field of degree , an integral ideal of , the prime ideal corresponding to the -adic topology on induced by . We assume that .
Definition 10** ([Da, Definitions 3.8, 3.9]).**
Let be a prime ideal of .
- (i)
We say is good for a cone if and if is a rational prime (i.e., the residue degree ). 2. (ii)
We say is good for a Shintani set if it can be expressed as a finite disjoint union of cones for which is good.
Definition 11** ([Da, Definitions 3.13, 3.16, Conjecture 3.21]).**
We take an element , a prime ideal , a Shintani domain satisfying the following conditions.
- (i)
Let be the order of in . We fix a generator satisfying , . 2. (ii)
* and .* 3. (iii)
The residue degree of and the ramification degree of . 4. (iv)
* is “simultaneously” good for in the following sense: There exist vectors , units satisfying*
[TABLE]
Remark 2**.**
Dasgupta [Da] took a suitable set of prime ideals instead of one prime ideal . In this article, we assume that for simplicity.
We denote by the completion of at , the ring of integers of respectively.
Definition 12** ([Da, Definitions 3.13, 3.17]).**
Let be as in Definition 11, a fractional ideal of relatively prime to . We put
[TABLE]
- (i)
For an open compact subset , a Shintani set , we put
[TABLE]
Here is defined in Definition 8. By [Da, Proposition 3.12] we see that
- •
When is good for , we have .
- •
When is good for and , we have . 2. (ii)
Assume that is good for and that . We define a -adic measure on by
[TABLE]
Under the assumption of Definition 11, is a -valued measure. 3. (iii)
For , we put
[TABLE]
Here denotes the narrow ray class field modulo . 4. (iv)
We define
[TABLE]
where . The product in the first line is actually a finite product since for all but finite .
Conjecture 3** ([Da, Conjecture 3.21]).**
Let be as in Definition 11, the fixed subfield of under .
- (i)
Let . For a fractional ideal relatively prime to satisfying , we put
[TABLE]
Then depends only on , not on the choices of . 2. (ii)
For any , is a -unit of satisfying . 3. (iii)
For any , we have .
5 The main results
We keep the notation in the previous sections: Let be a totally real field of degree , the narrow ray class field modulo . We assume that the prime ideal corresponding to the -adic topology on does not divide . Let be the fixed subfield of under . For , let be as in Definition 6. For a fractional ideal relatively prime to , let be as in Definition 12-(iv).
Theorem 1**.**
We have
[TABLE]
Corollary 1**.**
Conjecture 2* implies*
[TABLE]
where , , are the prime ideal of corresponding to the -adic topology on , the class number of , a generator of .
We prepare some Lemmas in order prove this Theorem.
Lemma 2** ([CN2, Théorème 13]).**
Let , , with roots of unity, . For , we have
[TABLE]
Here we put , with the binomial coefficient . The sum over is actually a finite sum since we have if is large enough.
Lemma 3**.**
Let be as in Definition 12-(i). Assume that is good for . Then we have
[TABLE]
Proof.
It is enough to show the statement when
- •
is a cone with , .
- •
is of the form (, ).
Put . By definition we have
[TABLE]
Let be a positive integer satisfying , . Then we have
[TABLE]
Since is a rational prime, the following homomorphism is a surjection.
[TABLE]
Here we denote the localization of at by . Hence for each , there exists an integer satisfying . Similarly we take satisfying and put . Then the following are equivalent:
[TABLE]
Let be a primitive th root of unity. We put , , . Note that for any . Then we have
[TABLE]
Here we put . It follows that
[TABLE]
Similarly we obtain
[TABLE]
By Lemma 2, we have for
[TABLE]
Then the assertion follows from (6), (7), (8), (9). ∎
Dasgupta’s -adic integration is originally associated with special values of multiple zeta functions “with the norm” . By the above Lemma, we can rewrite it in terms of special values of multiple zeta functions “without the norm” . This observation is one of the main discoveries in this paper.
Lemma 4**.**
Let , be as in Definition 12. Assume that is good for . Then we have for ,
[TABLE]
Here we put by using in (2).
Proof.
It is enough to show the statement when with , . By definition we can write
[TABLE]
[TABLE]
where are as in the proof of Lemma 3. On the other hand, by Lemma 2 again, we obtain
[TABLE]
By definition, we see that , for . It follows that
[TABLE]
Hence the first assertion is clear. The second assertion follows from the -adic interpolation property (4). ∎
Proof of Theorem 1.
For a fractional ideal , a Shintani set , an open compact subset , and for , we put
[TABLE]
whenever each function is well-defined. It suffices to show the following three equalities:
[TABLE]
Let , () be as in Definition 11-(iv). Since are fundamental domains of , we see that
[TABLE]
Namely we have
[TABLE]
By Lemma 3, we can write
[TABLE]
Therefore by Proposition 1-(i) we obtain
[TABLE]
We easily see that
[TABLE]
Hence, by Proposition 1-(i) again, we get
[TABLE]
Since , we have
[TABLE]
Then the assertion (11) follows from (5), (15), (16).
Next, differentiating (10) at , we obtain
[TABLE]
By definition, we have . Hence the assertion (12) is clear.
Finally we prove (13). Let be a Shintani domain . For each , we take an integral ideal satisfying , and put . By (5) we can write
[TABLE]
Since is the fixed subfield under , we may replace
[TABLE]
where denotes the image under , denotes the ideal class in of a fractional ideal . On the other hand, we can write for
[TABLE]
Therefore it suffices to show that we have for each
[TABLE]
We fix . Whenever , is constant, so we may put to be a fixed integral ideal . Then we have
[TABLE]
Let be a generator of the principal ideal . Then the following are equivalent:
s.t. .
Hence, taking a representative set of , we can write
[TABLE]
Namely we have for
[TABLE]
On the other hand, becomes another Shintani domain , and we can write for
[TABLE]
Then the assertion (17), replacing with , follows from (18), (19) and Proposition 1. We conclude the proof of (13) by showing that
[TABLE]
Note that the independence on the choice of is also discussed in [Da, §5.2] under certain conditions. Similarly to [Yo, Chap. III, Lemma 3.13], we see that there exist cones and units () which satisfy
[TABLE]
Therefore it suffices to show that
[TABLE]
It follows from Proposition 1 since . ∎
The reference list from the paper itself. Each links out to its DOI / PubMed record.
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- 2[CN 2] P. Cassou-Noguès, Valeurs aux entiers négative des fonction zêta et fonction zêta p 𝑝 p -adiques, Inv. Math. 51 (1979), 29–59.
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