1,038 research outputs found
Condensing Momentum Modes in 2-d 0A String Theory with Flux
We use a combination of conformal perturbation theory techniques and matrix
model results to study the effects of perturbing by momentum modes two
dimensional type 0A strings with non-vanishing Ramond-Ramond (RR) flux. In the
limit of large RR flux (equivalently, mu=0) we find an explicit analytic form
of the genus zero partition function in terms of the RR flux and the
momentum modes coupling constant alpha. The analyticity of the partition
function enables us to go beyond the perturbative regime and, for alpha>> q,
obtain the partition function in a background corresponding to the momentum
modes condensation. For momenta such that 0<p<2 we find no obstruction to
condensing the momentum modes in the phase diagram of the partition function.Comment: 22 page
'The Branch on which I sit' Heidi Safia Mirza in conversation with Yasmin Gunaratnam
This article is a conversation with Professor Heidi Mirza that discusses her experiences in Higher Education, intersectionality and renewed interest in black feminist ideas among new generations.
Heidi Safia Mirza’s work has been concerned with the local and geo-politics of gender, race, faith and culture. She has researched educational inequalities, including young black and Muslim women in school, and the workings of racialisation in higher education
The diagonalization method in quantum recursion theory
As quantum parallelism allows the effective co-representation of classical
mutually exclusive states, the diagonalization method of classical recursion
theory has to be modified. Quantum diagonalization involves unitary operators
whose eigenvalues are different from one.Comment: 15 pages, completely rewritte
Accuracy and Stability of Computing High-Order Derivatives of Analytic Functions by Cauchy Integrals
High-order derivatives of analytic functions are expressible as Cauchy
integrals over circular contours, which can very effectively be approximated,
e.g., by trapezoidal sums. Whereas analytically each radius r up to the radius
of convergence is equal, numerical stability strongly depends on r. We give a
comprehensive study of this effect; in particular we show that there is a
unique radius that minimizes the loss of accuracy caused by round-off errors.
For large classes of functions, though not for all, this radius actually gives
about full accuracy; a remarkable fact that we explain by the theory of Hardy
spaces, by the Wiman-Valiron and Levin-Pfluger theory of entire functions, and
by the saddle-point method of asymptotic analysis. Many examples and
non-trivial applications are discussed in detail.Comment: Version 4 has some references and a discussion of other quadrature
rules added; 57 pages, 7 figures, 6 tables; to appear in Found. Comput. Mat
Scaling limit of virtual states of triatomic systems
For a system with three identical atoms, the dependence of the wave
virtual state energy on the weakly bound dimer and trimer binding energies is
calculated in a form of a universal scaling function. The scaling function is
obtained from a renormalizable three-body model with a pairwise Dirac-delta
interaction. It was also discussed the threshold condition for the appearance
of the trimer virtual state.Comment: 9 pages, 3 figure
Tunneling of quantum rotobreathers
We analyze the quantum properties of a system consisting of two nonlinearly
coupled pendula. This non-integrable system exhibits two different symmetries:
a permutational symmetry (permutation of the pendula) and another one related
to the reversal of the total momentum of the system. Each of these symmetries
is responsible for the existence of two kinds of quasi-degenerated states. At
sufficiently high energy, pairs of symmetry-related states glue together to
form quadruplets. We show that, starting from the anti-continuous limit,
particular quadruplets allow us to construct quantum states whose properties
are very similar to those of classical rotobreathers. By diagonalizing
numerically the quantum Hamiltonian, we investigate their properties and show
that such states are able to store the main part of the total energy on one of
the pendula. Contrary to the classical situation, the coupling between pendula
necessarily introduces a periodic exchange of energy between them with a
frequency which is proportional to the energy splitting between
quasi-degenerated states related to the permutation symmetry. This splitting
may remain very small as the coupling strength increases and is a decreasing
function of the pair energy. The energy may be therefore stored in one pendulum
during a time period very long as compared to the inverse of the internal
rotobreather frequency.Comment: 20 pages, 11 figures, REVTeX4 styl
Entering the men's domain? Gender and portfolio allocation in European governments
While all government portfolios used to be the purview of men exclusively, more and more women are selected to sit around the cabinet table. But under which circumstances do women get appointed to different ministerial portfolios? This article, proposes a theoretical framework to consider how party leaders’ attitudes and motivations influence the allocation of portfolios to male and female ministers. These propositions are tested empirically by bringing together data on 7,005 cabinet appointments across 29 European countries from the late 1980s until 2014. Considering the key partisan dynamics of the ministerial selection process, it is found that women are significantly less likely to be appointed to the ‘core’ offices of state, and ‘masculine’ and ‘neutral’ policy areas. However, these gender differences are moderated by the ideology of the party that allocates them. Women are more likely to be appointed to ‘masculine’ portfolios when a party's voters have more progressive gender attitudes. This theoretical framework and analysis enhances our understanding of women's access to the government, which has important implications for how ministers are selected, as well as how women are represented in the most powerful policy?making positions in Europe
Hierarchical Spherical Model from a Geometric Point of View
A continuous version of the hierarchical spherical model at dimension d=4 is
investigated. Two limit distribution of the block spin variable X^{\gamma},
normalized with exponents \gamma =d+2 and \gamma =d at and above the critical
temperature, are established. These results are proven by solving certain
evolution equations corresponding to the renormalization group (RG)
transformation of the O(N) hierarchical spin model of block size L^{d} in the
limit L to 1 and N to \infty . Starting far away from the stationary Gaussian
fixed point the trajectories of these dynamical system pass through two
different regimes with distinguishable crossover behavior. An interpretation of
this trajectories is given by the geometric theory of functions which describe
precisely the motion of the Lee--Yang zeroes. The large-- limit of RG
transformation with L^{d} fixed equal to 2, at the criticality, has recently
been investigated in both weak and strong (coupling) regimes by Watanabe
\cite{W}. Although our analysis deals only with N=\infty case, it complements
various aspects of that work.Comment: 27 pages, 6 figures, submitted to Journ. Stat. Phy
Testing neutrino mass matrices with approximate L_e-L_mu-L_tau symmetry
As neutrino experiments are starting to probe the detailed structure of the
neutrino mass matrix, we present sumrules relating its matrix elements for a
class of models with approximate symmetry and the
observables in neutrino oscillation experiments. We show that regardless of how
the above symmetry is broken (whether in the neutrino sector or the charged
lepton sector), as long as the breaking terms are small, there is a lower bound
on the solar neutrino mixing angle, , correlated with the
solar mass difference square, , or the mixing parameter,
. We also discuss models where such patterns can arise.Comment: 11 pages, 3 figures; references and a note added; figure labelling
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