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事实证明,颜色/运动学的对偶性和双副本构造是获得引力理论新见识的系统工具。 在扩展我们以前的工作的同时,本文介绍了针对具有希格斯场的自发破碎的杨-米尔斯-爱因斯坦理论的新型双副本构造。 进入该结构的一个规范理论副本是自发破碎的(超级)Yang-Mills理论,而另一个副本是具有三线性标量相互作用的玻色杨-Mills标量理论,该对称性显示出明显的全局对称性。 我们表明,通过显示特定的附加李-代数关系,可以使这些量规理论的运动学分子服从颜色/运动学对偶。 我们详细讨论N = 2 $$ \ mathcal {N} = 2 $$超对称的显式示例,重点关注属于通用Jordan家族的Yang-Mills-Einstein超重力理论的四个维度和五个维度,并确定之间的映射。 超重力和双副本字段和参数。 我们还将简要讨论我们的结果在N = 4 $$ \ mathcal {N} = 4 $$超重力理论中的应用。 通过树级和单回路散射幅度的显式示例来说明这些构造。
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JHEP06(2017)064
Published for SISSA by Springer
Received: April 4, 2017
Accepted: May 1, 2017
Published: June 13, 2017
Spontaneously broken Yang-Mills-Einstein
supergravities as double copies
Marco Chiodaroli,
a,d
Murat G¨unaydin,
b
Henrik Johansson
c,d,e
and Radu Roiban
b,f
a
Max-Planck-Institut f¨ur Gravitationsphysik, Albert-Einstein-Institut,
Am M¨uhlenberg 1, 14476 Potsdam, Germany
b
Institute for Gravitation and the Cosmos, The Pennsylvania State University,
University Park PA 16802, U.S.A.
c
Theory Division, Physics Department, CERN,
CH-1211 Geneva 23, Switzerland
d
Department of Physics and Astronomy, Uppsala University,
SE-75108 Uppsala, Sweden
e
Nordita, KTH Royal Institute of Technology and Stockholm University,
Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
f
Kavli Institute for Theoretical Physics, University of California,
Santa Barbara, CA 93106-4030, U.S.A.
E-mail: marco.chiodaroli@physics.uu.se, mgunaydin@psu.edu,
henrik.johansson@physics.uu.se, adu@phys.psu.edu
Abstract: Color/kinematics duality and the double-copy construction have proved to be
systematic tools for gaining new insight into gravitational theories. Extending our ear-
lier work, in this paper we introduce new double-copy constructions for large classes of
spontaneously-broken Yang-Mills-Einstein theories with adjoint Higgs fields. One gauge-
theory copy entering the construction is a spontaneously-broken (super-)Yang-Mills theory,
while the other copy is a bosonic Yang-Mills-scalar theory with trilinear scalar interactions
that display an explicitly-broken global symmetry. We show that the kinematic numera-
tors of these gauge theories can be made to obey color/kinematics duality by exhibiting
particular additional Lie-algebraic relations. We discuss in detail explicit examples with
N = 2 supersymmetry, focusing on Yang-Mills-Einstein supergravity theories belonging to
the generic Jordan family in four and five dimensions, and identify the map between the
supergravity and double-copy fields and parameters. We also briefly discuss the application
of our results to N = 4 supergravity theories. The constructions are illustrated by explicit
examples of tree-level and one-loop scattering amplitudes.
Keywords: Extended Supersymmetry, Higgs Physics, Scattering Amplitudes, Supergrav-
ity Models
ArXiv ePrint: 1511.01740
Open Access,
c
The Authors.
Article funded by SCOAP
3
.
doi:10.1007/JHEP06(2017)064
JHEP06(2017)064
Contents
1 Introduction 1
2 Color/kinematics duality and double copy 3
2.1 Review: color/kinematics duality for complex representations 4
2.2 Scalar φ
3
theories 7
2.3 Yang-Mills-scalar theories: gauging G
c
9
2.4 Adjoint Higgs mechanism: breaking G
c
10
2.4.1 SU(N) examples 14
2.5 Explicit breaking of the global group G
k
15
2.5.1 SU(N) example 18
2.6 The double copy for spontaneously-broken theories 20
2.6.1 GR + YM = YM ⊗ (YM + φ
3
) 22
2.6.2 GR +
YM =
YM ⊗ (YM +
φ
3
) 23
3 Spontaneously-broken Yang-Mills-Einstein supergravity theories 24
3.1 Higgs mechanism in five-dimensional N = 2 YMESG theories 24
3.2 Higgs mechanism in four-dimensional N = 2 YMESG theories 28
4 Tree-level scattering amplitudes 32
4.1 Gauge theory amplitudes 32
4.1.1 Three points 32
4.1.2 Four points 33
4.2 Supergravity amplitudes 38
4.2.1 Three-point amplitudes and double-copy field map 38
4.2.2 Four-point amplitudes 40
5 Loop amplitudes 42
5.1 One-loop massless-scalar amplitude in broken YM + φ
3
theory 42
5.2 One-loop four-vector Yang-Mills-gravity amplitudes 46
6 N = 4 supergravity theories 49
6.1 N = 4 Maxwell-Einstein and Yang-Mills-Einstein supergravity theories 49
6.2 More on double copies with N = 4 supersymmetry 54
7 Conclusions and outlook 55
A Summary of index notation 57
B Symmetry breaking vs. dimensional compactification 58
B.1 Spontaneously broken SYM 58
B.2 Explicitly broken YM + φ
3
60
C Expansions for the supergravity Lagrangian 62
D Lagrangians of N = 4 MESG and YMESG theories in five dimensions 62
– i –
JHEP06(2017)064
1 Introduction
Einstein’s theory of gravity and spontaneously-broken gauge theory are two of the pillars of
our current understanding of the known fundamental interactions of Nature. While super-
symmetric field theories that combine gravitational interactions and spontaneous symmetry
breaking have been studied extensively at the Lagrangian level, the perturbative S matrices
of these theories have largely been unexplored.
Modern work on scattering amplitudes in matter-coupled gravitational theories has
been largely focused on pure supergravities and on cases in which additional matter consists
of abelian vectors (i.e. Maxwell-Einstein supergravities) or fermion/scalar fields. A key tool
has been the double-copy construction [1, 2], which has led to a dramatic simplification of
perturbative calculations. For example, explicit expressions of one-, two-, three- and four-
loop amplitudes have been obtained for N = 4, N = 5 and N = 8 supergravities in refs. [2–
14]. For the case of N ≤ 4, one-loop four-point superamplitudes have been obtained for the
generic Jordan family of N = 2 Maxwell-Einstein supergravity (MESG) theories [15–17],
for pure supergravities with N ≤ 4 [15, 17, 18], and for orbifolds thereof [15, 19].
The double-copy construction assumes the existence of presentations of gauge-theory
scattering amplitudes that exhibit color/kinematics duality. The duality states that, in
an amplitude’s Feynman-like diagrammatic expansion, one can find numerator factors
that obey Lie-algebraic kinematic relations mirroring the relations satisfied by the cor-
responding gauge-group color factors. Once found, the numerators may play the role of
these color factors in any gauge theory amplitude, and upon substitution one obtains valid
gravitational amplitudes. There is by now extensive evidence for the duality and for the
double-copy construction in wide classes of Yang-Mills (YM) theories and in the associated
(super)gravity theories. Examples where color/kinematics duality has been demonstrated
include: pure super-Yang-Mills (SYM) theories [1, 2, 20–22], SYM theories with adjoint
matter [15, 17, 18], self-dual Yang-Mills theory [23, 24], QCD and super-QCD [25, 26], YM
coupled to φ
3
theory [27], and YM theory extended by a higher-dimensional operator [28].
It has also been observed that the duality is not limited to YM gauge theories, but it also
applies to certain Chern-Simons-matter theories [29–31], as well as to the non-linear sigma
model/chiral Lagrangian [32] and to the closed (heterotic) sector of string theory [33].
Amplitudes in Maxwell-Einstein supergravities are obtained by a double-copy con-
struction of the form (pure SYM)⊗(YM coupled to scalars). Subgroups of the global
symmetries of Maxwell-Einstein supergravities can be gauged.
1
In the resulting theories
some of the vector fields become gauge fields of the chosen gauge group and transform in its
adjoint representation. Therefore, the only subgroups of the global symmetry that can be
gauged are those whose adjoint representation is smaller than the number of vector fields
that transform non-trivially under the global symmetry group. In five dimensions, gauging
only a subgroup of the global symmetry group in N = 2 Maxwell-Einstein supergravity
theories does not introduce a potential for the scalar fields and hence the resulting theory
is guaranteed to have a Minkowski vacuum state.
1
While gauging part of the R-symmetry group is very interesting, here we will focus on gaugings that
only affect the other global symmetries.
– 1 –
JHEP06(2017)064
The double-copy construction of a wide class of Yang-Mills-Einstein supergravity
(YMESG) theories was given in [27], where it was shown that one of the two gauge-
theory factors is a pure SYM theory, and the other is a bosonic YM theory coupled to
scalars that transforms in the adjoint representation of both the gauge group and a global
symmetry group. The latter theory has trilinear φ
3
couplings, and hence we refer to it as
YM + φ
3
theory. Through the double-copy construction, the global symmetry of the non-
supersymmetric gauge-theory factor becomes a local symmetry, and the trilinear scalar
couplings generate the minimal couplings of the corresponding gauge fields. The gravi-
tational supersymmetry is directly inherited from the SYM theory, thus accommodating
N = 1, 2, 4 YMESG theories and N = 0 Yang-Mills-Einstein (YME) theories. Earlier
work [34] introduced the same type of construction for single-trace tree-level YME ampli-
tudes. Recent work on YME amplitudes takes several different approaches, see refs. [35–41].
It is essential to explore the validity of the double-copy construction away from the
origin of the moduli space. In particular, a natural and physically-motivated extension
is to consider cases in which the supergravity gauge symmetry is spontaneously broken
through the Brout-Englert-Higgs mechanism. We will present such an extension in the
present paper. As a key result, we find that one of the two gauge-theory factors is the
spontaneously-broken pure SYM theory (or, alternatively stated, the Coulomb branch of
pure SYM theory), while the other is a particular massive deformation that explicitly
breaks the global symmetries of the YM + φ
3
theory.
Identifying the relation between asymptotic states of the supergravity theory and the
corresponding states of the gauge-theory factors is an important aspect of the double-
copy construction. For gauge theories with only adjoint fields, the double copy gives
a supergravity state for every tensor product of gauge-theory states (not counting the
degeneracy of the representation). In cases in which the gauge-theory matter transforms
in non-adjoint representations of the gauge group, the double-copy construction allows for
better tuning of the matter content of the gravitational theory, since only certain tensor
products of the gauge-theory matter are allowed.
In ref. [19] color/kinematics duality was extended to non-adjoint representations in
the context of orbifolds of N = 4 SYM, and the associated double copies were found to
be matter-coupled supergravity theories. The construction required that: (1) the gauge
groups of the two gauge theories should be identified, and (2) supergravity states corre-
spond to gauge-invariant bilinears that can be formed out of the gauge-theory states. This
construction correlates gauge- and global-group representations appearing in the resulting
gauge theories.
In ref. [17] color/kinematics duality was extended to theories with fields in the funda-
mental representation and used to construct pure N ≤ 4 supergravity theories as well as
matter-coupled theories. In this construction, the necessary condition for the double copy
to be valid is that the kinematic matter-dependent numerators obey the same relations
as the corresponding color factors with fundamental representations. Upon replacing the
color factors with kinematic numerator factors one similarly obtains a double copy that
correlates the representations of the states of the two gauge-theory sides.
For the double-copy constructions of supergravity theories with spontaneously-broken
gauge symmetry, the identification of the asymptotic states will follow closely the non-
– 2 –
JHEP06(2017)064
adjoint or fundamental cases. However, the details of the kinematic algebra obeyed by
the numerators will differ substantially compared to previous situations. The kinematic
Jacobi identities and commutation relations will be extended by additional identities which
are inherited from the Jacobi relations of the theory with unbroken gauge symmetry. We
stress that our construction works well with — but does not require — supersymmetry,
and similarly works in all dimensions in which the theories are defined, as it is expected
for color/kinematics duality.
The paper is organized as follows. In section 2 we review color/kinematics duality, and
identify matter-coupled gauge theories with fields in several different representations of the
gauge group and specific cubic and quartic couplings which obey the duality. We extend
color/kinematics duality and the double-copy construction to massive field theories, as well
as to field theories with spontaneously-broken gauge symmetry, paying close attention to
the construction of asymptotic states. In particular subsection 2.6 discusses extensions of
the double-copy construction and contains our main results of this generalization.
In section 4 we review, from the Lagrangian perspective, the Higgs mechanism in four-
and five-dimensional N = 2 Yang-Mills-Einstein supergravities. Such theories are uniquely
specified by their cubic interactions and provide simple examples of our construction. In
particular, we identify the four-dimensional symplectic frame in which the amplitudes from
the spontaneously-broken Yang-Mills-Einstein supergravity Lagrangian reproduce the ones
from the double-copy construction.
In section 5, we compute tree-level scattering amplitudes in the gauge theories dis-
cussed in section 3 and in the supergravity theories discussed in section 4. We find the
constraints imposed by color/kinematics duality on the cubic and quartic couplings of the
gauge theories, identify the precise map between supergravity states and gauge-invariant
billinears of gauge-theory states, and give the relation between the gauge-theory and su-
pergravity parameters.
In section 6, we discuss loop-level calculations in theories formulated in the earlier
sections. Section 7, discusses briefly spontaneously-broken N = 4 Yang-Mills-Einstein
supergravity theories. We review the bosonic part of their Lagrangians in five dimensions
and discuss how their amplitudes can be obtained through the double-copy construction
with a straightforward extension of the results obtained for N = 2 theories.
2 Color/kinematics duality and double copy
In this section, we review the color/kinematics duality applied to gauge theories that have
fields in complex representations of the gauge group. Giving concrete examples, we write
down Lagrangians of several gauge theories where the duality should be present. We then
spontaneously (and explicitly) break the symmetries of these theories, and in the process
generalize color/kinematics duality to such situations. Finally, we give the double-copy
prescription for spontaneously- and explicitly-broken theories.
– 3 –
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