276 research outputs found
Holographic non-relativistic fermionic fixed point and bulk dipole coupling
Inspired by the recently discovered non-relativistic fermionic fixed points,
we investigate how the presence of bulk dipole coupling modifies the spectral
function at one of these novel fixed points. As a result, although the infinite
flat band is always visible in the presence of the bulk dipole coupling as well
as chemical potential, the band is modified in a remarkable way at small
momenta up to the order of magnitude of bulk dipole coupling. On the other
hand, like a phoenix, a new Fermi surface sprouts from the formed gap when the
bulk dipole coupling is pushed up further such as to overshadow the charge
parameter, which is obviously different from what is found at the relativistic
fixed points.Comment: JHEP style, 1+17 pages, 9 figures, 1 table, typos corrected,
references added, version to appear in JHE
Generalized Konishi anomaly, Seiberg duality and singular effective superpotentials
Using the generalized Konishi anomaly (GKA) equations, we derive the
effective superpotential of four-dimensional N=1 supersymmetric SU(n) gauge
theory with n+2 fundamental flavors. We find, however, that the GKA equations
are only integrable in the Seiberg dual description of the theory, but not in
the direct description of the theory. The failure of integrability in the
direct, strongly coupled, description suggests the existence of
non-perturbative corrections to the GKA equations.Comment: 20 pages; v3: corrected the comparison to the SU(2) cas
The quantum mechanics of perfect fluids
We consider the canonical quantization of an ordinary fluid. The resulting
long-distance effective field theory is derivatively coupled, and therefore
strongly coupled in the UV. The system however exhibits a number of
peculiarities, associated with the vortex degrees of freedom. On the one hand,
these have formally a vanishing strong-coupling energy scale, thus suggesting
that the effective theory's regime of validity is vanishingly narrow. On the
other hand, we prove an analog of Coleman's theorem, whereby the semiclassical
vacuum has no quantum counterpart, thus suggesting that the vortex premature
strong-coupling phenomenon stems from a bad identification of the ground state
and of the perturbative degrees of freedom. Finally, vortices break the usual
connection between short distances and high energies, thus potentially
impairing the unitarity of the effective theory.Comment: 35 page
Holographic non-relativistic fermionic fixed point by the charged dilatonic black hole
Driven by the landscape of garden-variety condensed matter systems, we have
investigated how the dual spectral function behaves at the non-relativistic as
well as relativistic fermionic fixed point by considering the probe Dirac
fermion in an extremal charged dilatonic black hole with zero entropy. Although
the pattern for both of the appearance of flat band and emergence of Fermi
surface is qualitatively similar to that given by the probe fermion in the
extremal Reissner-Nordstrom AdS black hole, we find a distinctly different low
energy behavior around the Fermi surface, which can be traced back to the
different near horizon geometry. In particular, with the peculiar near horizon
geometry of our extremal charged dilatonic black hole, the low energy behavior
exhibits the universal linear dispersion relation and scaling property, where
the former indicates that the dual liquid is a Fermi one while the latter
implies that the dual liquid is not exactly of Landau Fermi type
On singular effective superpotentials in supersymmetric gauge theories
We study N=1 supersymmetric SU(2) gauge theory in four dimensions with a
large number of massless quarks. We argue that effective superpotentials as a
function of local gauge-invariant chiral fields should exist for these
theories. We show that although the superpotentials are singular, they
nevertheless correctly describe the moduli space of vacua, are consistent under
RG flow to fewer flavors upon turning on masses, and also reproduce by a
tree-level calculation the higher-derivative F-terms calculated by Beasely and
Witten (hep-th/0409149) using instanton methods. We note that this phenomenon
can also occur in supersymmetric gauge theories in various dimensions.Comment: 21 pages, 5 figures; minor errors correcte
Large-density field theory, viscosity, and "" singularities from string duals
We analyze systems where an effective large-N expansion arises naturally in
gauge theories without a large number of colors: a sufficiently large charge
density alone can produce a perturbative string ('tHooft) expansion. One
example is simply the well-known NS5/F1 system dual to , here viewed as a 5+1 dimensional theory at finite density. This model is
completely stable, and we find that the existing string-theoretic solution of
this model yields two interesting results. First, it indicates that the shear
viscosity is not corrected by effects in this system. For flow
perpendicular to the F1 strings the viscosity to entropy ratio take the usual
value , but for flow parallel to the F1's it vanishes as at low
temperature. Secondly, it encodes singularities in correlation functions coming
from low-frequency modes at a finite value of the momentum along the
directions. This may provide a strong coupling analogue of finite density
condensed matter systems for which fermionic constituents of larger operators
contribute so-called "" singularities. In the NS5/F1 example, stretched
strings on the gravity side play the role of these composite operators. We
explore the analogue for our system of the Luttinger relation between charge
density and the volume bounded by these singular surfaces. This model provides
a clean example where the string-theoretic UV completion of the gravity dual to
a finite density field theory plays a significant and calculable role.Comment: 28 pages. v2: added reference
Heterotic Vortex Strings
We determine the low-energy N=(0,2) worldsheet dynamics of vortex strings in
a large class of non-Abelian N=1 supersymmetric gauge theories.Comment: 44 pages, 3 figures. v2: typos corrected, reference adde
The Quantum Dynamics of Heterotic Vortex Strings
We study the quantum dynamics of vortex strings in N=1 SQCD with U(N_c) gauge
group and N_f=N_c quarks. The classical worldsheet of the string has N=(0,2)
supersymmetry, but this is broken by quantum effects. We show how the pattern
of supersymmetry breaking and restoration on the worldsheet captures the
quantum dynamics of the underlying 4d theory. We also find qualitative matching
of the meson spectrum in 4d and the spectrum on the worldsheet.Comment: 13 page
Small Amplitude Forced Fluid Dynamics from Gravity at T = 0
The usual derivative expansion of gravity duals of charged fluid dynamics is
known to break down in the zero temperature limit. In this case, the
fluid-gravity duality is not understood precisely. We explore this problem for
a zero temperature charged fluid driven by a low frequency, small amplitude and
spatially homogeneous external force. In the gravity dual, this corresponds to
time dependent boundary value of the dilaton. We calculate the bulk solution
for the dilaton and the leading backreaction to the metric and the gauge fields
using the modified low frequency expansion of [11]. The resulting solutions are
regular everywhere, establishing fluid-gravity duality to this order.Comment: 31 pages, Added comments in Sec.2 and Sec.4, Corrected typo
Bosonic excitations of the AdS4 Reissner-Nordstrom black hole
We study the long-lived modes of the charge density and energy density
correlators in the strongly-coupled, finite density field theory dual to the
AdS4 Reissner-Nordstrom black hole. For small momenta q<<\mu, these correlators
contain a pole due to sound propagation, as well as a pole due to a long-lived,
purely imaginary mode analogous to the \mu=0 hydrodynamic charge diffusion
mode. As the temperature is raised in the range T\lesssim\mu, the sound
attenuation shows no significant temperature dependence. When T\gtrsim\mu, it
quickly approaches the \mu=0 hydrodynamic result where it decreases like 1/T.
It does not share any of the temperature-dependent properties of the 'zero
sound' of Landau Fermi liquids observed in the strongly-coupled D3/D7 field
theory. For such small momenta, the energy density spectral function is
dominated by the sound mode at all temperatures, whereas the charge density
spectral function undergoes a crossover from being dominated by the sound mode
at low temperatures to being dominated by the diffusion mode when T \mu^2/q.
This crossover occurs due to the changing residue at each pole. We also compute
the momentum dependence of these spectral functions and their corresponding
long-lived poles at fixed, low temperatures T<<\mu.Comment: 33 pages, 21 figures, 6 animation
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