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在N = 4 $$ \ mathcal {N的模型中,我们给出了最一般的N = 4 $$ \ mathcal {N} = 4 $$,d = 1超共形对称D(2,1;α)的新的显式实现。 } = 4 $$超共形力学,基于可约化多重态(1,4,3)⊕(0,4,4),(3,4,1)⊕(0,4,4)和(4,4,0 )⊕(0,4,4)。 我们从这些系统的明显超对称超场作用开始,然后下降到相关的壳外作用,通过Noether过程推导D(2,1;α)(超)电荷。 讨论了D(2,1;α)这些实现的一些特殊性。 我们还通过连接多重数(3,4,1)和(4,4,0)来构造一个新的D(2,1;α)不变系统,这样它们通过一个额外的(0,0 4、4)多重。 由于消除了适当的辅助场,出现了新的铁离子共形偶合。
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JHEP10(2015)087
Published for SISSA by Springer
Received: August 26, 2015
Accepted: September 20, 2015
Published: October 14, 2015
New realizations of the supergroup D(2, 1; α) in
N = 4 superconformal mechanics
S. Fedoruk
1
and E. Ivanov
Bogoliubov Laboratory of Theoretical Physics, JINR,
141980 Dubna, Moscow Region, Russia
E-mail: fedoruk@theor.jinr.ru, eivanov@theor.jinr.ru
Abstract: We present new explicit realizations of the most general N = 4, d = 1 super-
conformal symmetry D(2, 1; α) in the models of N = 4 superconformal mechanics based
on the reduc i bl e multiplets (1, 4, 3) ⊕ (0, 4, 4), (3, 4, 1) ⊕ ( 0, 4, 4) and (4, 4, 0) ⊕ (0, 4, 4).
We start from the manifestly supersymmetric superfield actions for these systems and
then descend to the relevant off- and on-shell component actions from which we derive
the D(2, 1; α) ( super )charges by the Noether procedure. Some peculiarities of these real-
izations of D(2, 1; α) are discussed. We also construct a new D(2, 1; α) invariant system
by joining the multiplets (3, 4, 1) and (4, 4, 0) in such a way that they interact with each
other through an ext r a (0, 4, 4) multiplet. New fermionic conformal coupl i ngs appear as
the result of elimination of the appropriate auxiliary fields.
Keywords: Exte nd ed Supersymmetry, Superspaces, Conformal and W Symmetry
ArXiv ePrint:
1507.08584
1
On leave of absence from V.N. Karazin Kh a r kov National University, Ukraine.
Open Access,
c
The Authors.
Article funded by SCOAP
3
.
doi:
10.1007/JHEP10(2015)087
JHEP10(2015)087
Contents
1 Introduction
1
2 N = 4, d = 1 harmonic superspace 2
3 The fermionic multiplet (0, 4, 4) 4
4 The multiplet pair (1, 4, 3) ⊕ (0, 4, 4) 5
4.1 The multiplet (1, 4, 3) 5
4.2 Superconformal coupling of multiplets (1, 4, 3) and (0, 4, 4) 7
5 The multiplet pair (3, 4, 1) ⊕ (0, 4, 4) 11
5.1 The multiplet (3, 4, 1) 11
5.2 Superconformal coupling of the multiplets (3, 4, 1) and ( 0, 4, 4) 15
6 The multiplet pair (4, 4, 0) ⊕ (0, 4, 4) 20
6.1 The multiplet (4, 4, 0) 20
6.2 Superconformal couplings of the multiplets (4, 4, 0) and ( 0, 4, 4) 23
7 Superconformal coupling of the multiplets (1, 4, 3) and (4, 4, 0) mediated
by the multiplet (0, 4, 4)
26
8 Concluding remarks 29
1 Introduction
Superconformal mechanics (SCM) [
1]–[3] has plenty of applications [4, 5]–[31]. For instance,
the SCM models can be i d entified with the denom i nator theories in the AdS
2
/CFT
1
ver s i on
of the general AdS/CFT correspondence and used for the microscopic description of the
extremal black holes [
4, 5]–[10], [16, 30]. Various versions of the N = 4 SCM are of special
inte r e st i n these re spec ts , since they provide an explic i t descr i pt i on of the massive N = 4
superparticle moving n ear the horizon of an extre me Reissner-Nordstr¨om black hole (see,
e.g., [
4, 5, 7, 10, 30]). An i m portant class of the multiparticle SCM models is constituted by
inte gr abl e superconformal Calogero-type systems [
7, 15, 17, 18, 23]. A review of possible
implications of SCM in various domains, includ i ng N = 4 case, and additional references
can be found in [
26].
The most general N = 4, d = 1 superconformal group is the exceptional supergroup
D(2, 1; α) [
32, 33]. At α = 0, −1 it reduces to the semi-direct product PSU(1, 1|2) ⋊
SU(2) and at α = −
1
2
to the supergroup OSp(4|2) .
1
The reali z at i ons of D(2, 1; α)
1
The isomorphic superalgebras are related by the redefinition α → −(1 + α) .
– 1 –
JHEP10(2015)087
in the models of supersymmetric mechanics were a subjects of many works (see,
e.g., [
8, 9]–[14], [19]–[24, 25], [26–28, 31] and references therein).
2
As a rule, the realiza-
tions on one or another fixed type of the irreducible N = 4, d = 1 supermultiplet were
considered. Recently, the study of SU(1, 1|2) superconformal systems including some pairs
of such multiplets was initiated in ref. [
30]. Some interesting links with the N = 2, d = 5
supergrav i ty were established there. One of the basic points of the construction in [
30]
was the inclusion of couplings with the fermionic N = 4 multiplets (0, 4, 4) which do not
enlarge the dimen si on of the target bosonic manif ol d.
In the present pap e r we study the analogous realizations of D(2, 1; α) as distinct
from [ 30] , where the particular SU(1, 1|2) case was treated. Another new point of our
consideration is that in all cases we start from the manifestly N = 4 supersymmetr i c
off-shell superfield description of th e relevant multiplet pairs and write down the off-shell
component Lagr angi ans , while in [
30] only on-shell versions of the latter were addressed.
Keeping the relevant auxiliary fields in the combined actions of different pairs allows one
to get more general on-shell component actions after elimination of thes e fields by their
algebraic equations of motion.
3
Since the natural off-shel l description of the multiplets considered in [30] and in the
present paper is achieved in the framework of N = 4, d = 1 harmonic superspace [
36], we
start in section
2 with recalling the basics of this approach. Then, in section 3, we present
the superfield and component descriptions of the fermionic multiplet (0, 4, 4) , which is
the common p art of al l systems considered in [
30] and here . In section 4 we describe
the D(2, 1; α) invariant syst e m of interacting (1, 4, 3) and (0, 4, 4) multiplets, both in the
superfield and the component formulations, and give the precise form of the D(2, 1; α)
generators for this case. In sections
5 and 6 we do the same f or the multiplet pair (3, 4, 1)
and (0, 4, 4) , as well as for the pair (4, 4, 0) and (0, 4, 4) . In s ec t i on
7, as an example
of the power of the off-shell approach, we present a new superconformal system involving
the triple of the multiplets (1, 4, 3), (4, 4, 0) and (0, 4, 4). The elimination of the auxiliary
fields in the corresponding action yields new fermionic terms which are absent in the actions
of the relevant isolated pairs. Section 8 contains conclusions and outlook.
2 N = 4, d = 1 harmonic superspace
The harmonic analytic N=4, d = 1 superspace [36–38] as the one-dimensional versi on of
the general harmoni c superspace [
39–41] is defined as the following coordinate set
(ζ, u) = (t
A
, θ
+
,
¯
θ
+
, u
±
i
) , u
+i
u
−
i
= 1 . (2.1)
These coordinates are related to the standard N=4, d= 1 superspace (central basis) coor-
dinates z = (t, θ
i
,
¯
θ
i
), (
θ
i
) =
¯
θ
i
as
t
A
= t + i(θ
+
¯
θ
−
+ θ
−
¯
θ
+
), θ
±
= θ
i
u
±
i
,
¯
θ
±
=
¯
θ
i
u
±
i
. (2.2)
2
For implications of D(2, 1; α) in string theory and AdS/CFT correspondence see, e.g., [
34, 35].
3
As dist in c t from the D(2, 1; α) invariant systems with the so-called N = 4 spin multiplets [
20, 2 2 ], in
our case all boson ic fields of physical dimension are dynamical.
– 2 –
JHEP10(2015)087
The N=4 covariant spinor derivatives and their harmonic projections are defined by
D
i
=
∂
∂θ
i
− i
¯
θ
i
∂
t
,
¯
D
i
=
∂
∂
¯
θ
i
− iθ
i
∂
t
, (D
i
) = −
¯
D
i
, {D
i
,
¯
D
k
} = −2i δ
i
k
∂
t
, (2.3)
D
±
= u
±
i
D
i
,
¯
D
±
= u
±
i
¯
D
i
, {D
+
,
¯
D
−
} = −{D
−
,
¯
D
+
} = −2i ∂
t
A
. (2.4)
In the analytic basis z
A
= (t
A
, θ
±
,
¯
θ
±
, u
±i
), the derivatives D
+
and
¯
D
+
are short,
D
+
=
∂
∂θ
−
,
¯
D
+
= −
∂
∂
¯
θ
−
. (2.5)
The analyticity-preserving harmonic derivative D
++
and its conjugate D
−−
are given by
D
++
= ∂
++
+ 2iθ
+
¯
θ
+
∂
t
A
+ θ
+
∂
∂θ
−
+
¯
θ
+
∂
∂
¯
θ
−
,
D
−−
= ∂
−−
+ 2iθ
−
¯
θ
−
∂
t
A
+ θ
−
∂
∂θ
+
+
¯
θ
−
∂
∂
¯
θ
+
, ∂
±±
= u
±
i
∂
∂u
∓
i
, (2.6)
and become the pure partial derivatives ∂
±±
in the central basis. They satisfy the relations
[D
++
, D
−−
] = D
0
, [D
0
, D
±±
] = ±2D
±±
, (2.7)
where D
0
is the operator counting external harmonic U(1) charges. The integration mea-
sures in the full harmonic superspace and its analytic subsp ace are defined as
µ
H
= dudtd
4
θ = dudt
A
(D
−
¯
D
−
)(D
+
¯
D
+
) = µ
(−2)
A
(D
+
¯
D
+
) ,
µ
(−2)
A
= dudζ
(−2)
= dudt
A
dθ
+
d
¯
θ
+
= dudt
A
(D
−
¯
D
−
) . (2.8)
The analytic subspace (ζ, u) is closed under the action of the most general N = 4, d = 1
superconformal group D(2, 1; α) and its degener ate D(2, 1; α = 0) and D(2, 1; α = −1) cases
which are reduced to the semi-direct pr oducts PSU(1, 1|2) ⋊ SU(2)
ext
. In what follows, we
will need the transformation properties of some relevant quantities under the “Poincar´e”
and conformal supersymmetry. The invar i anc e under these transformations is sufficient for
ensuring the complete D(2, 1; α) invariance since the rest of the D(2, 1; α) transformations
is contained in the closure of the conformal and manifest Poincar´e N=4, d=1 supersym-
metries.
In the N=4 superfield approach, the invariance under the ordinary d = 1 supertrans-
lations (¯ε
i
=
(ε
i
))
δt = i(ε
k
¯
θ
k
− θ
k
¯ε
k
), δθ
k
= ε
k
, δ
¯
θ
k
= ¯ε
k
(2.9)
and
δt
A
= 2i(ε
−
¯
θ
+
− ¯ε
−
θ
+
), δθ
+
= ε
+
, δ
¯
θ
+
= ¯ε
+
, (2.10)
where ε
±
= ε
i
u
±
i
, ¯ε
±
= ¯ε
i
u
±
i
, is automatic.
– 3 –
JHEP10(2015)087
The coordinate reali z ati on of the superconformal D(2, 1; α) boosts is as follows:
δ
′
t = it(θ
k
¯η
k
+
¯
θ
k
η
k
) − (1 + α) θ
i
¯
θ
i
(θ
k
¯η
k
+
¯
θ
k
η
k
) , (2.11)
δ
′
θ
i
= −η
i
t − 2iα θ
i
(θ
k
¯η
k
) + 2i(1 + α) θ
i
(
¯
θ
k
η
k
) − i(1 + 2α) η
i
(θ
k
¯
θ
k
) , (2.12)
δ
′
¯
θ
i
= −¯η
i
t − 2iα
¯
θ
i
(
¯
θ
k
η
k
) + 2i(1 + α)
¯
θ
i
(θ
k
¯η
k
) + i(1 + 2α) ¯η
i
(θ
k
¯
θ
k
) , (2.13)
δ
′
t
A
= α
−1
Λ
sc
t
A
, δ
′
u
+
i
= Λ
++
u
−
i
, (2.14)
δ
′
θ
+
= −η
+
t
A
+ 2i(1 + α)η
−
θ
+
¯
θ
+
, δ
′
¯
θ
+
= −¯η
+
t
A
+ 2i(1 + α)¯η
−
θ
+
¯
θ
+
, (2.15)
δ
′
(dtd
4
θ) = −(dtd
4
θ) Λ
0
, δ
′
µ
H
= µ
H
(2Λ
sc
− (1 + α)Λ
0
) , δ
′
µ
(−2)
A
= 0 , (2.16)
δ
′
µ
(−2)
A
= 0 , δ
′
du = du D
−−
Λ
++
, (2.17)
δ
′
D
++
= −Λ
++
D
0
, δ
′
D
0
= 0 . (2.18)
Here η
±
= η
i
u
±
i
, ¯η
±
= ¯η
i
u
±
i
, ¯η
i
=
(η
i
) , and
Λ
sc
= 2iα(¯η
−
θ
+
− η
−
¯
θ
+
) , Λ
++
=D
++
Λ
sc
= 2iα(¯η
+
θ
+
− η
+
¯
θ
+
) , D
++
Λ
++
= 0 , ( 2. 19)
Λ
0
= α
−1
2Λ
sc
− D
−−
Λ
++
= 2i(θ
k
¯η
k
+
¯
θ
k
η
k
) , D
++
Λ
0
= 0 . (2.20)
The symbol ∼ means the generalized tilde-conjugation [
39–41]. With such definiti ons,
all the coordinate transformations contain no singularities in the degenerate α = 0 or
α = −1 cases.
3 The fermionic multiplet (0, 4, 4)
This multiplet is the fermionic analog of the multi p l et (4, 4, 0). It is described off shell
by the fermionic analytic superfiel d Ψ
+A
, A = 1, 2 ,
^
(Ψ
+A
) = Ψ
+
A
, satisfying the con-
straint [
36]:
D
++
Ψ
+A
= 0 ⇒ Ψ
+A
= φ
iA
u
+
i
+ θ
+
F
A
+
¯
θ
+
¯
F
A
− 2iθ
+
¯
θ
+
˙
φ
iA
u
−
i
, (3.1)
where (
φ
iA
) = −φ
iA
, (F
A
) =
¯
F
A
. On the index A, the appropriate SU(2)
P G
group
acts. Its generators commute with the N = 4 supersymmetry and D(2, 1; α) generators.
The r e q ui r e ment of superconformal covariance of the constrai nt (
3.1) uniquely fixes the
superconformal D(2, 1; α) transformation rule of Ψ
+A
, for any α, as
δ
sc
Ψ
+A
= Λ
sc
Ψ
+A
. (3.2)
Off-shell transformations of component fields are the following
δφ
iA
= −
ω
i
F
A
+ ¯ω
i
¯
F
A
,
δF
A
= 2i ¯ω
k
˙
φ
A
k
+ 2iα ¯η
k
φ
A
k
, δ
¯
F
A
= 2i ω
k
˙
¯
φ
k
A
+ 2iα η
k
¯
φ
k
A
,
(3.3)
where
ω
i
= ε
i
− t η
i
, ¯ω
i
= ¯ε
i
− t ¯η
i
.
– 4 –
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