Physics Letters B 776 (2018) 139–144
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Physics Letters B
www.elsevier.com/locate/physletb
Special geometry on the moduli space for the two-moduli non-Fermat
Calabi–Yau
Konstantin Aleshkin
a,b,∗
, Alexander Belavin
a,c,d
a
L.D. Landau Institute for Theoretical Physics, Akademika Semenova av. 1-A, Chernogolovka, 142432 Moscow region, Russia
b
International School of Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste, Italy
c
Department of Quantum Physics, Institute for Information Transmission Problems, Bolshoy Karetny per. 19, 127994 Moscow, Russia
d
Moscow Institute of Physics and Technology, Dolgoprudnyi, 141700 Moscow region, Russia
a r t i c l e i n f o a b s t r a c t
Article history:
Received
29 August 2017
Received
in revised form 10 October 2017
Accepted
15 November 2017
Available
online 21 November 2017
Editor:
M. Cveti
ˇ
c
We clarify the recently proposed method for computing a special Kähler metric on a Calabi–Yau complex
structure moduli space using the fact that the moduli space is a subspace of a particular Frobenius
manifold. We use this method to compute a previously unknown special Kähler metric in a two-moduli
non-Fermat model.
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
To find the low-energy Lagrangian of string theory compacti-
fied
on a Calabi–Yau (CY) manifold X, one must know the special
Kähler geometry on the moduli space of the CY manifold [1–4].
An alternative method for computing the Kähler potential in the
case where the CY manifold is given by a hypersurface W
0
(x) = 0
in
a weighted projective space was recently presented in [5]. In
this paper, we briefly review this method and use it to compute
the special Kähler geometry on the moduli space of a two-moduli
non-Fermat threefold considered in [6]. This approach is based on
the fact that the moduli space of a CY manifold is a subspace in
the particular Frobenius manifold (FM) [7] that arises from the de-
formation
space of the singularity defined by the LG superpotential
W
0
(x). In this paper, we discuss this FM and its connection with
the geometry of the CY moduli space in more detail.
It
is known, that an isolated singularity W
0
(x) defines an ob-
ject
called a Milnor ring R
0
, Endowed with an invariant pairing
this ring becomes a Frobenius algebra. Its elements define versal
deformations of the singularity. It is well known that the space
of deformations admits a FM structure. In our case, W
0
(x) is a
quasihomogeneous polynomial, which defines a CY manifold in
the weighted projective space. For our purposes of computation
of the CY moduli space geometry we actually need the Frobenius
subalgebra R
Q
0
of R
0
, that is multiplicatively generated only by
polynomials of the same degree d as W
0
(x). These polynomials are
related to the complex structure deformations. The subalgebra R
Q
0
*
Corresponding author.
E-mail
address: kaleshkin@sissa.it (K. Aleshkin).
consists of elements of degrees 0, d, 2d and 3d, and each homo-
geneous
component of this algebra is naturally a subgroup of the
respective middle Hodge cohomology H
3,0
(X ), H
2,1
(X ), H
1,2
(X )
and H
0,3
(X ). In our examples, R
Q
0
is actually isomorphic to H
3
(X ).
The FM in which we are interested is precisely the submanifold of
the FM on the versal deformations of W
0
(X ) restricted to the de-
formations
by the elements of R
Q
0
.
The
relation to the FM structure allows obtaining the follow-
ing
explicit expression [5] for the Kähler potential in terms of the
holomorphic FM metric η
μν
in the flat coordinates and periods of
the holomorphic 3-form :
e
−K
= σ
+
μ
(φ)η
μρ
M
ν
ρ
σ
−
ν
(φ), M = T
−1
¯
T . (1)
Here, φ is a parameter on the moduli space, and σ
±
ν
(φ) are periods
of the holomorphic 3-form , defined below as the integrals of
over some special basis of cycles γ
μ
in the homology group H
3
(X ),
which are defined in terms of the connection with the FM.
The
constant nondegenerate complex matrix T connects the ba-
sis
σ
±
ν
(φ) with another basis ω
±
μ
(φ) defined in [8,6] as integrals of
over another special basis of the cycles q
ν
by the linear relation
ω
±
μ
(φ) = T
ν
μ
σ
±
ν
(φ). (2)
The explicit expression for the Kähler potential is obtained as fol-
lows.
The basis ω
μ
is defined as integrals over the homology cycles
q
μ
with real coefficients. These cycles have a well-defined inter-
section
matrix C
μν
= q
μ
∩ q
ν
. The matrix M and formula (1) are
independent of the specific choice of ω
μ
. The Kähler potential
K (φ) on the moduli space with the coordinates φ and the holo-
morphic
FM metric η
αβ
can be expressed in the terms of C
μν
, the
https://doi.org/10.1016/j.physletb.2017.11.030
0370-2693/
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.