Physics Letters B 781 (2018) 238–243
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Scalar one-point functions and matrix product states of AdS/dCFT
Marius de Leeuw
a
, Charlotte Kristjansen
b,∗
, Georgios Linardopoulos
c,d
a
School of Mathematics & Hamilton Mathematics Institute, Trinity College Dublin, Dublin, Ireland
b
Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
c
Institute of Nuclear and Particle Physics, N.C.S.R. “Demokritos”, 153 10 Agia Paraskevi, Greece
d
Department of Physics, National and Kapodistrian University of Athens, Zografou Campus, 157 84 Athens, Greece
a r t i c l e i n f o a b s t r a c t
Article history:
Received
28 February 2018
Accepted
28 March 2018
Available
online 4 April 2018
Editor:
N. Lambert
Keywords:
AdS/CFT
correspondence
Defect
CFT
Probe
branes
One-point
functions
SO(6)
spin chain
Matrix
product states
We determine in a closed form all scalar one-point functions of the defect CFT dual to the D3–D5 probe
brane system with k units of flux which amounts to calculating the overlap between a Bethe eigenstate
of the integrable SO(6) spin chain and a certain matrix product state of bond dimension k. In particular,
we show that the matrix product state is annihilated by all the parity odd charges of the spin chain
which has recently been suggested as the criterion for such a state to correspond to an integrable initial
state. Finally , we discuss the properties of the analogous matrix product state for the SO(5) symmetric
D3–D7 probe brane set-up.
© 2018 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
Matrix product states continue to make their appearance in yet
more diverse problems in theoretical physics. In a series of recent
works matrix product states were used to obtain a convenient re-
formulation
of the problem of calculating one-point functions in
certain defect versions of N = 4SYM[1–4]. More precisely, the
tree-level one-point functions of the defect CFT could be expressed
as the overlap between a matrix product state and a Bethe eigen-
state
of an integrable spin chain. By a matrix product state we
understand a state of the form
i
tr[A
i
i
...A
i
L
]|e
i
1
...e
i
L
, (1)
where the e
i
take values among the basis vectors in an appropri-
ate
Hilbert space and the A
j
are matrices of size d × d where d
is
the bond dimension. Matrix product states can be considered a
special class of initial states for quantum quenches in integrable
lattice models and have been studied from this perspective f.inst.
in [5,6]. In this connection the object of interest is simply the over-
*
Corresponding author.
E-mail
addresses: mdeleeuw @maths .tcd .ie (M. de Leeuw), kristjan @nbi .dk
(C. Kristjansen),
glinard @inp .demokritos .gr (G. Linardopoulos).
lap between the given initial state and the Bethe eigenstates of the
integrable system as these quantities provide input for the study
of the relaxation properties of the system after a quench. A num-
ber
of overlap formulas have appeared for the case of the XXZ
Heisenberg spin chain. In [7] formulas for the overlap between a
Bethe eigenstate and respectively the Néel state, the dimer state
and the q-deformed dimer state were derived. Later it was shown
that these formulas could be expressed in terms of determinants
built out of Bethe roots [8,9] and the result was generalized to
the m’th raised version of the Néel state [10]. The Néel state, the
dimer state and the q -deformed dimer state are all examples of
so-called two-site product states, i.e. states of even length which
can be built by tensoring identical two-site states. Recently, an ex-
pression
for the overlap between any such two-site product state
and a Bethe eigenstate of the XXZ spin chain was presented [11].
The
study of one-point functions of non-protected operators in
the defect version of N = 4SYM dual to the D3–D5 probe brane
system with k units of background gauge field flux has sparked the
derivation of overlap formulas involving matrix product states. An
example of a matrix product state which is of relevance for these
considerations is the following state of the SU(2) or Heisenberg
XXX spin chain
|MPS=tr
L
l=1
|↑ ⊗
t
1
+|↓⊗t
2
,
(2)
https://doi.org/10.1016/j.physletb.2018.03.083
0370-2693/
© 2018 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
.