74,511 research outputs found
Constraints on Hidden Photon Models from Electron g-2 and Hydrogen Spectroscopy
The hidden photon model is one of the simplest models which can explain the
anomaly of the muon anomalous magnetic moment (g-2). The experimental
constraints are studied in detail, which come from the electron g-2 and the
hydrogen transition frequencies. The input parameters are set carefully in
order to take dark photon contributions into account and to prevent the
analysis from being self-inconsistent. It is shown that the new analysis
provides a constraint severer by more than one order of magnitude than the
previous result.Comment: 18 pages, 2 figures, 1 table. v2: minor correction
Luttinger liquid physics from infinite-system DMRG
We study one-dimensional spinless fermions at zero and finite temperature T
using the density matrix renormalization group. We consider nearest as well as
next-nearest neighbor interactions; the latter render the system inaccessible
by a Bethe ansatz treatment. Using an infinite-system alogrithm we demonstrate
the emergence of Luttinger liquid physics at low energies for a variety of
static correlation functions as well as for thermodynamic properties. The
characteristic power law suppression of the momentum distribution n(k) function
at T=0 can be directly observed over several orders of magnitude. At finite
temperature, we show that n(k) obeys a scaling relation. The Luttinger liquid
parameter and the renormalized Fermi velocity can be extracted from the density
response function, the specific heat, and/or the susceptibility without the
need to carry out any finite-size analysis. We illustrate that the energy scale
below which Luttinger liquid power laws manifest vanishes as the half-filled
system is driven into a gapped phase by large interactions
Topological invariants of time-reversal-invariant band structures
The topological invariants of a time-reversal-invariant band structure in two
dimensions are multiple copies of the invariant found by Kane
and Mele. Such invariants protect the topological insulator and give rise to a
spin Hall effect carried by edge states. Each pair of bands related by time
reversal is described by a single invariant, up to one less than
half the dimension of the Bloch Hamiltonians. In three dimensions, there are
four such invariants per band. The invariants of a crystal
determine the transitions between ordinary and topological insulators as its
bands are occupied by electrons. We derive these invariants using maps from the
Brillouin zone to the space of Bloch Hamiltonians and clarify the connections
between invariants, the integer invariants that underlie the
integer quantum Hall effect, and previous invariants of -invariant
Fermi systems.Comment: 4 page
Recommended from our members
Financial liberalisation in India and a new test of the complementarity hypothesis
This paper reappraises the financial repression hypothesis for India in the light of the partial liberalisation of the financial sector in the early 1990s, using for the first time, state-of-art multivariate cointegration and vector error correction models (VECM). From this robust test we find that for the Indian economy over the sample period 1951-1999 money and capital are complementary, suggesting that higher real interest rates will raise the demand for money and lead to higher levels of investment. Furthermore, testing for a structural break in the early 1990s – to coincide with the liberalisation of the financial sector in India – suggests that these reforms have not significantly changed the complementary relationship between money and capital. The policy implication is that further financial liberalisation is required in India, to enhance investment and economic growth
Recommended from our members
An investigation into the sources of fluctuation in real and nominal wage rates in eight EU countries: A structural VAR approach
This paper uses the SVAR approach to assess the degree of labor market flexibility –measured as the responsiveness of real and nominal wages to permanent and temporary shocks - in eight EU member states (France, Italy, UK, Netherlands, Poland, Hungary, Slovakia and the Czech Republic) with a view to assessing their suitability for Euro-area membership. It is found that for Hungary and the Czech Republic real wages are more responsive to real (permanent) shocks than some current members of the Euro zone, such as Italy. On the other hand, in Poland and Slovakia, real wage flexibility seems to be extremely low, making higher unemployment more likely than other EU countries and early euro-area membership unadvisable
Doping dependence of thermopower and thermoelectricity in strongly correlated systems
The search for semiconductors with high thermoelectric figure of merit has
been greatly aided by theoretical modeling of electron and phonon transport,
both in bulk materials and in nanocomposites. Recent experiments have studied
thermoelectric transport in ``strongly correlated'' materials derived by doping
Mott insulators, whose insulating behavior without doping results from
electron-electron repulsion, rather than from band structure as in
semiconductors. Here a unified theory of electrical and thermal transport in
the atomic and ``Heikes'' limit is applied to understand recent transport
experiments on sodium cobaltate and other doped Mott insulators at room
temperature and above. For optimal electron filling, a broad class of
narrow-bandwidth correlated materials are shown to have power factors (the
electronic portion of the thermoelectric figure of merit) as high at and above
room temperature as in the best semiconductors.Comment: 4 pages, 4 figure
Approaching Many-Body Localization from Disordered Luttinger Liquids via the Functional Renormalization Group
We study the interplay of interactions and disorder in a one-dimensional
fermion lattice coupled adiabatically to infinite reservoirs. We employ both
the functional renormalization group (FRG) as well as matrix product state
techniques, which serve as an accurate benchmark for small systems. Using the
FRG, we compute the length- and temperature-dependence of the conductance
averaged over samples for lattices as large as sites. We
identify regimes in which non-ohmic power law behavior can be observed and
demonstrate that the corresponding exponents can be understood by adapting
earlier predictions obtained perturbatively for disordered Luttinger liquids.
In presence of both disorder and isolated impurities, the conductance has a
universal single-parameter scaling form. This lays the groundwork for an
application of the functional renormalization group to the realm of many-body
localization
- …