404 research outputs found
Mirror symmetry for N=1 QED in three dimensions
We construct three-dimensional N=1 QED with N_f flavors using branes of type
IIB string theory. This theory has a mirror, which can be realized using the
S-dual brane configuration. As in examples with more supersymmetry, the Higgs
branch of the original theory gets mapped into the Coulomb branch of the
mirror. We use parity invariance to argue that these branches cannot be lifted
by quantum corrections.Comment: 10 pages, Latex, 1 figure, reference adde
Absence of a VVDZ Discontinuity in AdS_AdS
We clarify the role of gauge invariance for the theory of an AdS4 brane
embedded in AdS5. The presence of a nonvanishing mass parameter even for the
lightest KK mode of the graviton indicates that all of the spin-2 modes
propagate five polarization states. Despite this fact, it was shown earlier
that the classical theory has a smooth limit as the mass parameter is taken to
zero. We argue that locality in the fifth dimension ensures that this property
survives at the quantum level.Comment: 4 pages, Revtex; discussion of why VVDZ is not a problem even at the
quantum level is change
Dynamic trapping near a quantum critical point
The study of dynamics in closed quantum systems has recently been revitalized
by the emergence of experimental systems that are well-isolated from their
environment. In this paper, we consider the closed-system dynamics of an
archetypal model: spins near a second order quantum critical point, which are
traditionally described by the Kibble-Zurek mechanism. Imbuing the driving
field with Newtonian dynamics, we find that the full closed system exhibits a
robust new phenomenon -- dynamic critical trapping -- in which the system is
self-trapped near the critical point due to efficient absorption of field
kinetic energy by heating the quantum spins. We quantify limits in which this
phenomenon can be observed and generalize these results by developing a
Kibble-Zurek scaling theory that incorporates the dynamic field. Our findings
can potentially be interesting in the context of early universe physics, where
the role of the driving field is played by the inflaton or a modulus.Comment: 4 pages, 3 figures + 5 page supplemen
Solving 2D QCD with an adjoint fermion analytically
We present an analytic approach to solving 1+1 dimensional QCD with an
adjoint Majorana fermion. In the UV this theory is described by a trivial CFT
containing free fermions. The quasi-primary operators of this CFT lead to a
discrete basis of states which is useful for diagonalizing the Hamiltonian of
the full strongly interacting theory. Working at large-, we find that the
decoupling of high scaling-dimension quasi-primary operators from the
low-energy spectrum occurs exponentially fast in their scaling-dimension. This
suggests a scheme, whereby, truncating the basis to operators of dimension
below , one can calculate the low-energy spectrum, parametrically
to an accuracy of (although the precise accuracy depends on
the state). Choosing we find very good agreement with the
known spectrum obtained earlier by numerical DLCQ methods. Specifically, below
the first three-particle threshold, we are able to identify all six
single-particle bound-states, as well as several two-particle thresholds.Comment: 26 pages, 5 figures; v2: some typos correcte
Numerical Investigations of SO(4) Emergent Extended Symmetry in Spin-1/2 Heisenberg Antiferromagnetic Chains
The antiferromagnetic Heisenberg chain is expected to have an extended
symmetry, [SU(2)xSU(2)]/Z 2 , in the infrared limit, whose physical
interpretation is that the spin and dimer order parameters form the components
of a common 4-dimensional vector. Here we numerically in- vestigate this
emergent symmetry using quantum Monte Carlo simulations of a modified
Heisenberg chain (the J-Q model) in which the logarithmic scaling corrections
of the conventional Heisenberg chain can be avoided. We show how the two- and
three-point spin and dimer correlation func- tions approach their forms
constrained by conformal field theory as the system size increases and
numerically confirm the expected effects of the extended symmetry on various
correlation functions
Five-branes, Seven-branes and Five-dimensional E_n field theories
We generalize the (p,q) 5-brane web construction of five-dimensional field
theories by introducing (p,q) 7-branes, and apply this construction to theories
with a one-dimensional Coulomb branch. The 7-branes render the exceptional
global symmetry of these theories manifest. Additionally, 7-branes allow the
construction of all E_n theories up to n=8, previously not possible in 5-brane
configurations. The exceptional global symmetry in the field theory is a
subalgebra of an affine symmetry on the 7-branes, which is necessary for the
existence of the system. We explicitly determine the quantum numbers of the BPS
states of all E_n theories using two simple geometrical constraints.Comment: 28 pages, LaTeX, 8 figure
A Conformal Truncation Framework for Infinite-Volume Dynamics
We present a new framework for studying conformal field theories deformed by
one or more relevant operators. The original CFT is described in infinite
volume using a basis of states with definite momentum, , and conformal
Casimir, . The relevant deformation is then considered using
lightcone quantization, with the resulting Hamiltonian expressed in terms of
this CFT basis. Truncating to states with , one can numerically find the resulting spectrum, as well
as other dynamical quantities, such as spectral densities of operators. This
method requires the introduction of an appropriate regulator, which can be
chosen to preserve the conformal structure of the basis. We check this
framework in three dimensions for various perturbative deformations of a free
scalar CFT, and for the case of a free CFT deformed by a mass term and a
non-perturbative quartic interaction at large-. In all cases, the truncation
scheme correctly reproduces known analytic results. We also discuss a general
procedure for generating a basis of Casimir eigenstates for a free CFT in any
number of dimensions.Comment: 48+37 pages, 17 figures; v2: references added, small clarification
Nonperturbative Matching Between Equal-Time and Lightcone Quantization
We investigate the nonperturbative relation between lightcone (LC) and
standard equal-time (ET) quantization in the context of theory
in . We discuss the perturbative matching between bare parameters and the
failure of its naive nonperturbative extension. We argue that they are
nevertheless the same theory nonperturbatively, and that furthermore the
nonperturbative map between bare parameters can be extracted from ET
perturbation theory via Borel resummation of the mass gap. We test this map by
using it to compare physical quantities computed using numerical Hamiltonian
truncation methods in ET and LC.Comment: 22+8 pages, 10 figure
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