262 research outputs found
Symmetric scalars
We provide a complete classification of Poincar\'e-invariant scalar field
theories with an enlarged set of classical symmetries to leading order in
derivatives, namely for the so-called theories, in two or more
spacetime dimensions. We find only three possibilities: Dirac-Born-Infeld,
Cuscuton and Scaling theories. The latter two classes of actions involve an
arbitrary function of the scalar field. As an application, we use the scaling
symmetry to derive an infinite set of constraints on the Wilsonian coefficients
of the low-energy Effective Field Theory. Furthermore, we study the extension
of these results to cosmological (FLRW) and (Anti-)de Sitter spacetimes. We
find in particular that the Cuscuton action has a generic set of symmetries
around any background spacetime that possesses Killing vector fields, while the
DBI actions have well-known analogues that we summarize explicitly
Spatial curvature at the sound horizon
The effect of spatial curvature on primordial perturbations is controlled by  ΩK,0/cs2 , where  ΩK,0 is today's fractional density of spatial curvature and  cs is the speed of sound during inflation. Here we study these effects in the limit  cs≪ 1 . First, we show that the standard cosmological soft theorems in flat universes are violated in curved universes and the soft limits of correlators can have non-universal contributions even in single-clock inflation. This is a consequence of the fact that, in the presence of spatial curvature, there is a gap between the spectrum of residual diffeomorphisms and that of physical modes. Second, there are curvature corrections to primordial correlators, which are not scale invariant. We provide explicit formulae for these corrections to the power spectrum and the bispectrum to linear order in curvature in single-clock inflation. We show that the large-scale CMB anisotropies could provide interesting new constraints on these curvature effects, and therefore on  ΩK,0/cs2 , but it is necessary to go beyond our linear-order treatment
Categorical Landau Paradigm for Gapped Phases
We propose a unified framework to classify gapped infra-red (IR) phases with
categorical symmetries, leading to a generalized, categorical Landau paradigm.
This is applicable in any dimension and gives a succinct, comprehensive, and
computationally powerful approach to classifying gapped symmetric phases. The
key tool is the symmetry topological field theory (SymTFT), which is a one
dimension higher TFT with two boundaries, which we choose both to be
topological. We illustrate the general idea for (1+1)d gapped phases with
categorical symmetries and suggest higher-dimensional extensions.Comment: 4 pages + supplementary materia
Gapped Phases with Non-Invertible Symmetries: (1+1)d
We propose a general framework to characterize gapped infra-red (IR) phases
of theories with non-invertible (or categorical) symmetries. In this paper we
focus on (1+1)d gapped phases with fusion category symmetries. The approach
that we propose uses the Symmetry Topological Field Theory (SymTFT) as a key
input: associated to a field theory in d spacetime dimensions, the SymTFT lives
in one dimension higher and admits a gapped boundary, which realizes the
categorical symmetries. It also admits a second, physical, boundary, which is
generically not gapped. Upon interval compactification of the SymTFT by
colliding the gapped and physical boundaries, we regain the original theory. In
this paper, we realize gapped symmetric phases by choosing the physical
boundary to be a gapped boundary condition as well. This set-up provides
computational power to determine the number of vacua, the symmetry breaking
pattern, and the action of the symmetry on the vacua. The SymTFT also
manifestly encodes the order parameters for these gapped phases, thus providing
a generalized, categorical Landau paradigm for (1+1)d gapped phases. We find
that for non-invertible symmetries the order parameters involve multiplets
containing both untwisted and twisted sector local operators, and hence can be
interpreted as mixtures of conventional and string order parameters. We also
observe that spontaneous breaking of non-invertible symmetries can lead to
vacua that are physically distinguishable: unlike the standard symmetries
described by groups, non-invertible symmetries can have different actions on
different vacua of an irreducible gapped phase. This leads to the presence of
relative Euler terms between physically distinct vacua. We also provide a
mathematical description of symmetric gapped phases as 2-functors from
delooping of fusion category characterizing the symmetry to Euler completion of
2-vector spaces.Comment: 139 pages, v2: corrected an omission in the analysis of TY(Z_N)
gapped phases reported by A. Antinucci, references adde
Nonsupersymmetric brane vacua in stabilized compactifications
We derive the equations for the nonsupersymmetric vacua of D3-branes in the
presence of nonperturbative moduli stabilization in type IIB flux
compactifications, and solve and analyze them in the case of two particular
7-brane embeddings at the bottom of the warped deformed conifold. In the limit
of large volume and long throat, we obtain vacua by imposing a constraint on
the 7-brane embedding. These vacua fill out continuous spaces of higher
dimension than the corresponding supersymmetric vacua, and have negative
effective cosmological constant. Perturbative stability of these vacua is
possible but not generic. Finally, we argue that anti-D3-branes at the tip of
the conifold share the same vacua as D3-branes.Comment: 17 pages, 1 figure, LaTeX. v2: references added, typo fixed. v3:
version appearing in JHE
Chasing Brane Inflation in String-Theory
We investigate the embedding of brane anti-brane inflation into a concrete
type IIB string theory compactification with all moduli fixed. Specifically, we
are considering a D3-brane, whose position represents the inflaton , in a
warped conifold throat in the presence of supersymmetrically embedded D7-branes
and an anti D3-brane localized at the tip of the warped conifold cone. After
presenting the moduli stabilization analysis for a general D7-brane embedding,
we concentrate on two explicit models, the Ouyang and the Kuperstein
embeddings. We analyze whether the forces, induced by moduli stabilization and
acting on the D3-brane, might cancel by fine-tuning such as to leave us with
the original Coulomb attraction of the anti D3-brane as the driving force for
inflation. For a large class of D7-brane embeddings we obtain a negative
result. Cancelations are possible only for very small intervals of
around an inflection point but not globally. For the most part of its motion
the inflaton then feels a steep, non slow-roll potential. We study the
inflationary dynamics induced by this potential.Comment: 34 pages, 4 figures. Final version published in JCA
Conformal consistency relations for single-field inflation
We generalize the single-field consistency relations to capture not only the
leading term in the squeezed limit---going as 1/q^3, where q is the small
wavevector---but also the subleading one, going as 1/q^2. This term, for an
(n+1)-point function, is fixed in terms of the variation of the n-point
function under a special conformal transformation; this parallels the fact that
the 1/q^3 term is related with the scale dependence of the n-point function.
For the squeezed limit of the 3-point function, this conformal consistency
relation implies that there are no terms going as 1/q^2. We verify that the
squeezed limit of the 4-point function is related to the conformal variation of
the 3-point function both in the case of canonical slow-roll inflation and in
models with reduced speed of sound. In the second case the conformal
consistency conditions capture, at the level of observables, the relation among
operators induced by the non-linear realization of Lorentz invariance in the
Lagrangian. These results mean that, in any single-field model, primordial
correlation functions of \zeta are endowed with an SO(4,1) symmetry, with
dilations and special conformal transformations non-linearly realized by \zeta.
We also verify the conformal consistency relations for any n-point function in
models with a modulation of the inflaton potential, where the scale dependence
is not negligible. Finally, we generalize (some of) the consistency relations
involving tensors and soft internal momenta.Comment: 26 pages, 1 figure. v2. Corrected typos, notably a sign error in eq.
(54). Matches JCAP published versio
DBI Inflation using a One-Parameter Family of Throat Geometries
We demonstrate the possibility of examining cosmological signatures in the
DBI inflation setup using the BGMPZ solution, a one-parameter family of
geometries for the warped throat which interpolate between the Maldacena-Nunez
and Klebanov-Strassler solutions. The warp factor is determined numerically and
subsequently used to calculate cosmological observables including the scalar
and tensor spectral indices, for a sample point in the parameter space. As one
moves away from the KS solution for the throat the warp factor is qualitatively
different, which leads to a significant change for the observables, but also
generically increases the non-Gaussianity of the models. We argue that the
different models can potentially be differentiated by current and future
experiments.Comment: 17 pages, 10 figures; v2: section 4 expanded, references added; v3:
typos fixe
Universality in D-brane Inflation
We study the six-field dynamics of D3-brane inflation for a general scalar
potential on the conifold, finding simple, universal behavior. We numerically
evolve the equations of motion for an ensemble of more than 7 \times 10^7
realizations, drawing the coefficients in the scalar potential from statistical
distributions whose detailed properties have demonstrably small effects on our
results. When prolonged inflation occurs, it has a characteristic form: the
D3-brane initially moves rapidly in the angular directions, spirals down to an
inflection point in the potential, and settles into single-field inflation. The
probability of N_{e} e-folds of inflation is a power law, P(N_{e}) \propto
N_{e}^{-3}, and we derive the same exponent from a simple analytical model. The
success of inflation is relatively insensitive to the initial conditions: we
find attractor behavior in the angular directions, and the D3-brane can begin
far above the inflection point without overshooting. In favorable regions of
the parameter space, models yielding 60 e-folds of expansion arise
approximately once in 10^3 trials. Realizations that are effectively
single-field and give rise to a primordial spectrum of fluctuations consistent
with WMAP, for which at least 120 e-folds are required, arise approximately
once in 10^5 trials. The emergence of robust predictions from a six-field
potential with hundreds of terms invites an analytic approach to multifield
inflation.Comment: 28 pages, 9 figure
- …