12,511 research outputs found
Interacting topological phases in multiband nanowires
We show that semiconductor nanowires coupled to an s-wave superconductor
provide a playground to study effects of interactions between different
topological superconducting phases supporting Majorana zero-energy modes. We
consider quasi-one dimensional system where the topological phases emerge from
different transverse subbands in the nanowire. In a certain parameter space, we
show that there is a multicritical point in the phase diagram where the
low-energy theory is equivalent to the one describing two coupled Majorana
chains. We study effect of interactions as well as symmetry-breaking
perturbations on the topological phase diagram in the vicinity of this
multicritical point. Our results shed light on the stability of the topological
phase around the multicritical point and have important implications for the
experiments on Majorana nanowires.Comment: 8 pages, 2 figures; final version to appear in PR
Model B4 : multi-decade creep and shrinkage prediction of traditional and modern concretes
To improve the sustainability of concrete infrastructure, engineers face the challenge of incorporating new concrete materials while pushing the expected design life beyond 100 years. The time-dependent creep and shrinkage response of concrete governs the serviceability and durability in this multi-decade time frame. It has been shown that current prediction equations for creep and shrinkage underestimate material deformations observed in structures outside of a laboratory environment. A new prediction model for creep and shrinkage is presented that can overcome some of the shortcomings of the current equations. The model represents an extension and systematic recalibration of model B3, a 1995 RILEM Recommendation, which derives its functional form from the phenomena of diffusion, chemical hydration, moisture sorption, and the evolution of micro-stresses in the cement structure. The model is calibrated through a joint optimization of a new enlarged laboratory test database and a new database of bridge deflection records to overcome the bias towards short-term behavior. A framework for considering effects of aggregates, admixtures, additives, and higher temperatures is also incorporated
CP4 miracle: shaping Yukawa sector with CP symmetry of order four
We explore the phenomenology of a unique three-Higgs-doublet model based on
the single CP symmetry of order 4 (CP4) without any accidental symmetries. The
CP4 symmetry is imposed on the scalar potential and Yukawa interactions,
strongly shaping both sectors of the model and leading to a very characteristic
phenomenology. The scalar sector is analyzed in detail, and in the Yukawa
sector we list all possible CP4-symmetric structures which do not run into
immediate conflict with experiment, namely, do not lead to massless or
mass-degenerate quarks nor to insufficient mixing or CP-violation in the CKM
matrix. We show that the parameter space of the model, although very
constrained by CP4, is large enough to comply with the electroweak precision
data and the LHC results for the 125 GeV Higgs boson phenomenology, as well as
to perfectly reproduce all fermion masses, mixing, and CP violation. Despite
the presence of flavor changing neutral currents mediated by heavy Higgs
scalars, we find through a parameter space scan many points which accurately
reproduce the kaon CP-violating parameter as well as oscillation
parameters in K and mesons. Thus, CP4 offers a novel minimalistic
framework for building models with very few assumptions, sufficient predictive
power, and rich phenomenology yet to be explored.Comment: 39 pages, 8 figures, 1 table; v2: expanded discussion, extra
references, matches published versio
Fine asymptotic behavior in eigenvalues of random normal matrices: Ellipse Case
We consider the random normal matrices with quadratic external potentials
where the associated orthogonal polynomials are Hermite polynomials and the
limiting support (called droplet) of the eigenvalues is an ellipse. We
calculate the density of the eigenvalues near the boundary of the droplet up to
the second subleading corrections and express the subleading corrections in
terms of the curvature of the droplet boundary. From this result we
additionally get the expected number of eigenvalues outside the droplet. We
also obtain the asymptotics of the kernel and found that, in the bulk, the
correction term is exponentially small. This leads to the vanishing of certain
Cauchy transform of the orthogonal polynomial in the bulk of the droplet up to
an exponentially small error.Comment: 39 pages, 5 figures. Extended version: Theorem 1.2, Theorem 1.4,
Section 6 and Section 7.3 are ne
Wave packet evolution in non-Hermitian quantum systems
The quantum evolution of the Wigner function for Gaussian wave packets
generated by a non-Hermitian Hamiltonian is investigated. In the semiclassical
limit this yields the non-Hermitian analog of the Ehrenfest
theorem for the dynamics of observable expectation values. The lack of
Hermiticity reveals the importance of the complex structure on the classical
phase space: The resulting equations of motion are coupled to an equation of
motion for the phase space metric---a phenomenon having no analog in Hermitian
theories.Comment: Example added, references updated, 4 pages, 2 figure
Aging to Equilibrium Dynamics of SiO2
Molecular dynamics computer simulations are used to study the aging dynamics
of SiO2 (modeled by the BKS model). Starting from fully equilibrated
configurations at high temperatures T_i =5000K/3760K the system is quenched to
lower temperatures T_f=2500K, 2750K, 3000K, 3250K and observed after a waiting
time t_w. Since the simulation runs are long enough to reach equilibrium at
T_f, we are able to study the transition from out-of-equilibrium to equilibrium
dynamics. We present results for the partial structure factors, for the
generalized incoherent intermediate scattering function C_q(t_w, t_w+t), and
for the mean square displacement msd(t_w,t_w+t). We conclude that there are
three different t_w regions: (I) At very short waiting times, C_q(t_w, t_w+t)
decays very fast without forming a plateau. Similarly msd(t_w,t_w+t) increases
without forming a plateau. (II) With increasing t_w a plateau develops in
C_q(t_w, t_w+t) and msd(t_w,t_w+t). For intermediate waiting times the plateau
height is independent of t_w and T_i. Time superposition applies, i.e.
C_q=C_q(t/t_r) where t_r=t_r(t_w) is a waiting time dependent decay time.
Furthermore C_q=C(q,t_w,t_w+t) scales as C_q=C(q,z(t_w,t) where z is a function
of t_w and t only, i.e. independent of q. (III) At large t_w the system reaches
equilibrium, i.e. C_q(t_w,t_w+t) and msd(t_w,t_w+t) are independent of t_w and
T_i. For C_q(t_w,t_w+t) we find that the time superposition of intermediate
waiting times (II) includes the equilibrium curve (III).Comment: 9 pages, 11 figures, submission to PR
Some new results concerning the vacuum in Dirac Hole Theory
In Dirac's hole theory the vacuum state is generally believed to be the state
of minimum energy. It will be shown that this is not, in fact, the case and
that there must exist states in hole theory with less energy than the vacuum
state. It will be shown that energy can be extracted from the hole theory
vacuum state through the application of an electric field.Comment: Accepted by Physica Scripta, 19 page
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