1,773 research outputs found
D-wave correlated Critical Bose Liquids in two dimensions
We develop a description of a new quantum liquid phase of interacting bosons
in 2d which possesses relative D-wave two-body correlations and which we call a
D-wave Bose Liquid (DBL). The DBL has no broken symmetries, supports gapless
boson excitations residing on "Bose surfaces" in momentum space, and exhibits
power law correlations with continuously variable exponents. While the DBL can
be constructed for bosons in the 2d continuum, the state only respects the
point group symmetries of the square lattice. On the lattice the DBL respects
all symmetries and does not require a particular filling. But lattice effects
allow a second distinct phase, a quasi-local variant which we call a D-wave
Local Bose Liquid (DLBL). Remarkably, the DLBL has short-range boson
correlations and hence no Bose surfaces, despite sharing gapless excitations
and other critical signatures with the DBL. Moreover, both phases are metals
with a resistance that vanishes as a power of the temperature. We establish
these results by constructing a class of many-particle wavefunctions for the
DBL, which are time reversal invariant analogs of Laughlin's quantum Hall
wavefunction for bosons at . A gauge theory formulation leads to a
simple mean field theory, and an N-flavor generalization enables incorporation
of gauge field fluctuations to deduce the properties of the DBL/DLBL; various
equal time correlation functions are in qualitative accord with the properties
inferred from the wavefunctions. We also identify a promising Hamiltonian which
might manifest the DBL or DLBL, and perform a variational study comparing to
other competing phases. We suggest how the DBL wavefunction can be generalized
to describe an itinerant non-Fermi liquid phase of electrons on the square
lattice with a no double occupancy constraint, a D-wave metal phase.Comment: 33 pages, 17 figure
Seeing the Invisible Axion in the Sparticle Spectrum
I describe how under favourable circumstances the invisible axion may
manifest its existence at the LHC through the sparticle spectrum; in particular
through a gluino \sim \ln (M_P/m_{3/2}) times heavier than other gauginos.Comment: 4 pages, REVTe
Cosmic String Evolution in Higher Dimensions
We obtain the equations of motion for cosmic strings in extensions of the 3+1
FRW model with extra dimensions. From these we derive a generalisation of the
Velocity-dependent One-Scale (VOS) model for cosmic string network evolution
which we apply, first, to a higher-dimensional isotropic FRW model and,
second, to a 3+1 FRW model with static flat extra dimensions. In the former
case the string network does not achieve a scaling regime because of the
diminishing rate of string intersections (), but this can be avoided in
the latter case by considering compact, small extra dimensions, for which there
is a reduced but still appreciable string intercommuting probability. We note
that the velocity components lying in the three expanding dimensions are
Hubble-damped, whereas those in the static extra dimensions are only very
weakly damped. This leads to the pathological possibility, in principle, that
string motion in the three infinite dimensions can come to a halt preventing
the strings from intersecting, with the result that scaling is not achieved and
the strings irreversibly dominate the early universe. We note criteria by which
this can be avoided, notably if the spatial structure of the network becomes
essentially three-dimensional, as is expected for string networks produced in
brane inflation. Applying our model to a brane inflation setting, we find
scaling solutions in which the effective 3D string motion does not necessarily
stop, but it is slowed down because of the excitations trapped in the extra
dimensions. These effects are likely to influence cosmic string network
evolution for a long period after formation and we discuss their more general
implications.Comment: 23 pages, 8 figures. Minor updates and notational clarification
Topological Insulators and Superconductors from String Theory
Topological insulators and superconductors in different spatial dimensions
and with different discrete symmetries have been fully classified recently,
revealing a periodic structure for the pattern of possible types of topological
insulators and supercondutors, both in terms of spatial dimensions and in terms
of symmetry classes. It was proposed that K-theory is behind the periodicity.
On the other hand, D-branes, a solitonic object in string theory, are also
known to be classified by K-theory. In this paper, by inspecting low-energy
effective field theories realized by two parallel D-branes, we establish a
one-to-one correspondence between the K-theory classification of topological
insulators/superconductors and D-brane charges. In addition, the string theory
realization of topological insulators and superconductors comes naturally with
gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a
gauge field theory of topological nature, such as ones with the Chern-Simons
term or the -term in various dimensions. This sheds light on
topological insulators and superconductors beyond non-interacting systems, and
the underlying topological field theory description thereof. In particular, our
string theory realization includes the honeycomb lattice Kitaev model in two
spatial dimensions, and its higher-dimensional extensions. Increasing the
number of D-branes naturally leads to a realization of topological insulators
and superconductors in terms of holography (AdS/CFT).Comment: 13 pages, 3 figures;references update
Normal ordering and non(anti)commutativity in open super strings
Nonanticommutativity in an open super string moving in the presence of a
background antisymmetric tensor field is investigated
in a conformal field theoretic approach, leading to nonanticommutative
structures. In contrast to several discussions, in which boundary conditions
are taken as Dirac constraints, we first obtain the mode algebra by using the
newly proposed normal ordering, which satisfies both equations of motion and
boundary conditions. Using these the anticommutator among the fermionic string
coordinates is obtained. Interestingly, in contrast to the bosonic case, this
new normal ordering plays an important role in uncovering the underlying
nonanticommutative structure between the fermionic string coordinates. We feel
that our approach is more transparent than the previous ones and the results we
obtain match with the existing results in the literature.Comment: Comments 10 pages latex, accepted for publication in Physical Review
Gravireggeons and transplanckian scattering in models with one extra dimension
The inelastic scattering of the brane fields induced by -channel
gravireggeons exchanges in the RS model with a small curvature is
considered, and the imaginary part of the eikonal is analytically calculated.
It is demonstrated that the results can be obtained from the corresponding
formulae previously derived in the ADD model with one extra dimension of the
size by formal replacement . The inelastic
cross section for the scattering of ultra-high neutrino off the nucleon is
numerically estimated for the case TeV, where
is a reduced Planck scale in five warped dimensions.Comment: 17 pages, LaTeX2e, 3 eps figure
Supersymmetric Pair Correlation Function of Wilson Loops
We give a path integral derivation of the annulus diagram in a supersymmetric
theory of open and closed strings with Dbranes. We compute the pair correlation
function of Wilson loops in the generic weakly coupled supersymmetric flat
spacetime background with Dbranes. We obtain a -u^4/r^9 potential between heavy
nonrelativistic sources in a supersymmetric gauge theory at short distances.Comment: 18 pages, Revte
Dual Actions for Born-Infeld and Dp-Brane Theories
Dual actions with respect to U(1) gauge fields for Born-Infeld and -brane
theories are reexamined. Taking into account an additional condition, i.e. a
corollary to the field equation of the auxiliary metric, one obtains an
alternative dual action that does not involve the infinite power series in the
auxiliary metric given by ref. \cite{s14}, but just picks out the first term
from the series formally. New effective interactions of the theories are
revealed. That is, the new dual action gives rise to an effective interaction
in terms of one interaction term rather than infinite terms of different
(higher) orders of interactions physically. However, the price paid for
eliminating the infinite power series is that the new action is not quadratic
but highly nonlinear in the Hodge dual of a -form field strength. This
non-linearity is inevitable to the requirement the two dual actions are
equivalent.Comment: v1: 11 pages, no figures; v2: explanation of effective interactions
added; v3: concision made; v4: minor modification mad
New twist field couplings from the partition function for multiply wrapped D-branes
We consider toroidal compactifications of bosonic string theory with
particular regard to the phases (cocycles) necessary for a consistent
definition of the vertex operators, the boundary states and the T-duality
rules. We use these ingredients to compute the planar multi-loop partition
function describing the interaction among magnetized or intersecting D-branes,
also in presence of open string moduli. It turns out that unitarity in the open
string channel crucially depends on the presence of the cocycles. We then focus
on the 2-loop case and study the degeneration limit where this partition
function is directly related to the tree-level 3-point correlators between
twist fields. These correlators represent the main ingredient in the
computation of Yukawa couplings and other terms in the effective action for
D-brane phenomenological models. By factorizing the 2-loop partition function
we are able to compute the 3-point couplings for abelian twist fields on
generic non-factorized tori, thus generalizing previous expressions valid for
the 2-torus.Comment: 36 pages, 1 figure; v2: typos corrected, proof in the Appendix
improve
Gauge and gravitational interactions of non-BPS D-particles
We study the gauge and gravitational interactions of the stable non-BPS
D-particles of the type I string theory. The gravitational interactions are
obtained using the boundary state formalism while the SO(32) gauge interactions
are determined by evaluating disk diagrams with suitable insertions of boundary
changing (or twist) operators. In particular the gauge coupling of a D-particle
is obtained from a disk with two boundary components produced by the insertion
of two twist operators. We also compare our results with the amplitudes among
the non-BPS states of the heterotic string which are dual to the D-particles.
After taking into account the known duality and renormalization effects, we
find perfect agreement, thus confirming at a non-BPS level the expectations
based on the heterotic/type I duality.Comment: LaTeX File, 29 pages, 3 figures, two references added. Final version
to be published in Nucl. Phys.
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