565 research outputs found
Topological Exchange Statistics in One Dimension
The standard topological approach to indistinguishable particles formulates
exchange statistics by using the fundamental group to analyze the connectedness
of the configuration space. Although successful in two and more dimensions,
this approach gives only trivial or near trivial exchange statistics in one
dimension because two-body coincidences are excluded from configuration space.
Instead, we include these path-ambiguous singular points and consider
configuration space as an orbifold. This orbifold topological approach allows
unified analysis of exchange statistics in any dimension and predicts novel
possibilities for anyons in one-dimensional systems, including non-abelian
anyons obeying alternate strand groups. These results clarify the
non-topological origin of fractional statistics in one-dimensional anyon
models.Comment: v3: major revision and expansion from last edition; 16 pgs., 5 figs.,
109 ref
Entanglement for all quantum states
It is shown that a state that is factorizable in the Hilbert space
corresponding to some choice of degrees of freedom, becomes entangled for a
different choice of degrees of freedom. Therefore, entanglement is not a
special case but is ubiquitous in quantum systems. Simple examples are
calculated and a general proof is provided. The physical relevance of the
change of tensor product structure is mentioned.Comment: 9 page
Limits on entanglement in rotationally-invariant scattering of spin systems
This paper investigates the dynamical generation of entanglement in
scattering systems, in particular two spin systems that interact via
rotationally-invariant scattering. The spin degrees of freedom of the in-states
are assumed to be in unentangled, pure states, as defined by the entropy of
entanglement. Because of the restriction of rotationally-symmetric
interactions, perfectly-entangling S-matrices, i.e. those that lead to a
maximally entangled out-state, only exist for a certain class of separable
in-states. Using Clebsch-Gordan coefficients for the rotation group, the
scattering phases that determine the S-matrix are determined for the case of
spin systems with , 1, and 3/2.Comment: 6 pages, no figures; v.2: sections added, edited for clarity,
conclusions and calculation unchanged, typos corrected; v.3: new abstrct,
revised first two sections, added reference
Beyond braid anyons: A lattice model for one-dimensional anyons with a Galilean invariant continuum limit
Anyonic exchange statistics can emerge when the configuration space of
quantum particles is not simply-connected. Most famously, anyon statistics
arises for particles with hard-core two-body constraints in two dimensions.
Here, the exchange paths described by the braid group are associated to
non-trivial geometric phases, giving rise to abelian braid anyons. Hard-core
three-body constraints in one dimension (1D) also make the configuration space
of particles non-simply connected, and it was recently shown that this allows
for a different form of anyons with statistics given by the traid group instead
of the braid group. In this article we propose a first concrete model for such
traid anyons. We first construct a bosonic lattice model with number-dependent
Peierls phases which implement the desired geometric phases associated with
abelian representations of the traid group and then define anyonic operators so
that the Hamiltonian becomes local and quadratic with respect to them. The
ground-state of this traid-anyon-Hubbard model shows various indications of
emergent approximate Haldane exclusion statistics. The continuum limit results
in a Galilean invariant Hamiltonian with eigenstates that correspond to
previously constructed continuum traid-anyonic wave functions. This provides
not only an a-posteriori justification of our model, but also shows that our
construction serves as an intuitive approach to traid anyons. Moreover, it
contrasts with the non-Galilean invariant continuum limit of the anyon-Hubbard
model [Keilmann et al., Nat.\ Comm.~\textbf{2}, 361 (2011)] describing braid
anyons on a discrete 1D configuration space. We attribute this difference to
the fact that (unlike braid anyons) traid anyons are well defined also in the
continuum in 1D.Comment: 24 pages, 15 figure
Understanding entangled spins in QED
The stability of two entangled spins dressed by electrons is studied by
calculating the scattering phase shifts. The interaction between electrons is
interpreted by fully relativistic QED and the screening effect is described
phenomenologically in the Debye exponential form . Our results
show that if the (Einstein-Podolsky-Rosen-) EPR-type states are kept stable
under the interaction of QED, the spatial wave function must be
parity-dependent. The spin-singlet state and the polarized state along the z-axis\QTR{bf}{\}give rise to two
different kinds of phase shifts\QTR{bf}{.} Interestingly, the interaction
between electrons in the spin-singlet pair is found to be attractive. Such an
attraction could be very useful when we extract the entangled spins from
superconductors. A mechanism to filter the entangled spins is also discussed.Comment: 6 pages, 3 figures. changes adde
Recommended from our members
The impact of prior platinum therapy on survival in patients with metastatic urothelial cancer receiving vinflunine
Background: A phase III trial demonstrated an overall survival advantage with the addition of vinflunine to best supportive care (BSC) in platinum-refractory advanced urothelial cancer. We subsequently examined the impact of an additional 2 years of survival follow-up and evaluated the influence of first-line platinum therapy on survival. Methods: The 357 eligible patients from the phase III study were categorised into two cohorts depending on prior cisplatin treatment: cisplatin or non-cisplatin. Survival was calculated using the Kaplan–Meier method. Results: The majority had received prior cisplatin (70.3%). Survival was higher in the cisplatin group (HR: 0.76; CI 95% 0.58–0.99; P=0.04) irrespective of treatment arm. Multivariate analysis including known prognostic factors (liver involvement, haemoglobin, performance status) and prior platinum administration did not show an independent effect of cisplatin. Vinflunine reduced the risk of death by 24% in the cisplatin-group (HR: 0.76; CI 95% 0.58–0.99; P=0.04) and by 35% in non-cisplatin patients (HR: 0.65; CI 95% 0.41–1.04; P=0.07). Interpretation: Differences in prognostic factors between patients who can receive prior cisplatin and those who cannot may explain the survival differences in patients who undergo second line therapy. Prior cisplatin administration did not diminish the subsequent benefit of vinflunine over BSC
Time of metastatic disease presentation and volume of disease are prognostic for metastatic hormone sensitive prostate cancer (mHSPC)
Impurity Effect on the In-plane Penetration Depth of the Organic Superconductors -(BEDT-TTF) ( = Cu(NCS) and Cu[N(CN)]Br)
We report the in-plane penetration depth of single
crystals -(BEDT-TTF) ( Cu(NCS) and Cu[N(CN)]Br) by
means of the reversible magnetization measurements under the control of
cooling-rate. In = Cu(NCS), as an
extrapolation toward = 0 K does not change by the cooling-rate within the
experimental accuracy, while is slightly reduced. On the other
hand, in = Cu[N(CN)]Br, indicates a distinct
increase by cooling faster. The different behavior of
on cooling-rate between the two salts is quantitatively explained in terms of
the local-clean approximation (London model), considering that the former salt
belongs to the very clean system and the later the moderate clean one. The good
agreement with this model demonstrates that disorders of ethylene-group in
BEDT-TTF introduced by cooling faster increase the
electron(quasiparticle)-scattering, resulting in shorter mean free path.Comment: 8 pages, 9 figure
- …