3,429 research outputs found
Natural Scherk-Schwarz Theories of the Weak Scale
Natural supersymmetric theories of the weak scale are under growing pressure
given present LHC constraints, raising the question of whether untuned
supersymmetric (SUSY) solutions to the hierarchy problem are possible. In this
paper, we explore a class of 5-dimensional natural SUSY theories in which SUSY
is broken by the Scherk-Schwarz mechanism. We pedagogically explain how
Scherk-Schwarz elegantly solves the traditional problems of 4-dimensional SUSY
theories (based on the MSSM and its many variants) that usually result in an
unsettling level of fine-tuning. The minimal Scherk-Schwarz set up possesses
novel phenomenology, which we briefly outline. We show that achieving the
observed physical Higgs mass motivates extra structure that does not
significantly affect the level of tuning (always better than ) and
we explore three qualitatively different extensions: the addition of extra
matter that couples to the Higgs, an extra gauge group under
which the Higgs is charged and an NMSSM-like solution to the Higgs mass
problem.Comment: 36 pages + appendix, 12 figure
Quantum gas mixtures in different correlation regimes
We present a many-body description for two-component ultracold bosonic gases
when one of the species is in the weakly interacting regime and the other is
either weakly or strongly interacting. In the one-dimensional limit the latter
case system is a hybrid in which a Tonks-Girardeau gas is immersed in a
Bose-Einstein condensate, which is an example of a new class of quantum system
involving a tunable, superfluid environment. We describe the process of phase
separation microscopically and semiclassically in both situations and show that
the quantum correlations are maintained in the separated phase.Comment: 4 pages, 3 figure
Vortex macroscopic superpositions in ultracold bosons in a double-well potential
We study macroscopic superpositions in the orbital rather than the spatial
degrees of freedom, in a three-dimensional double-well system. We show that the
ensuing dynamics of interacting excited ultracold bosons, which in general
requires at least eight single-particle modes and Fock
vectors, is described by a surprisingly small set of many-body states. An
initial state with half the atoms in each well, and purposely excited in one of
them, gives rise to the tunneling of axisymmetric and transverse vortex
structures. We show that transverse vortices tunnel orders of magnitude faster
than axisymmetric ones and are therefore more experimentally accessible. The
tunneling process generates macroscopic superpositions only distinguishable by
their orbital properties and within experimentally realistic times.Comment: 9 pages, 6 figure
Heat current control in trapped BEC
We investigate the heat transport and the control of heat current among two
spatially separated trapped Bose-Einstein Condensates (BEC), each of them at a
different temperature. To allow for heat transport among the two independent
BECs we consider a link made of two harmonically trapped impurities, each of
them interacting with one of the BECs. Since the impurities are spatially
separated, we consider long-range interactions between them, namely a
dipole-dipole coupling. We study this system under theoretically suitable and
experimentally feasible assumptions/parameters. The dynamics of these
impurities is treated within the framework of the quantum Brownian motion
model, where the excitation modes of the BECs play the role of the heat bath.
We address the dependence of heat current and current-current correlations on
the physical parameters of the system. Interestingly, we show that heat
rectification, i.e., the unidirectional flow of heat, can occur in our system,
when a periodic driving on the trapping frequencies of the impurities is
considered. Therefore, our system is a possible setup for the implementation of
a phononic circuit. Motivated by recent developments on the usage of BECs as
platforms for quantum information processing, our work offers an alternative
possibility to use this versatile setting for information transfer and
processing, within the context of phononics, and more generally in quantum
thermodynamics.Comment: 33 pages, 4 Figure
Tunneling, self-trapping and manipulation of higher modes of a BEC in a double well
We consider an atomic Bose-Einstein condensate trapped in a symmetric
one-dimensional double well potential in the four-mode approximation and show
that the semiclassical dynamics of the two ground state modes can be strongly
influenced by a macroscopic occupation of the two excited modes. In particular,
the addition of the two excited modes already unveils features related to the
effect of dissipation on the condensate. In general, we find a rich dynamics
that includes Rabi oscillations, a mixed Josephson-Rabi regime, self-trapping,
chaotic behavior, and the existence of fixed points. We investigate how the
dynamics of the atoms in the excited modes can be manipulated by controlling
the atomic populations of the ground states.Comment: 12 pages, 5 figure
The key role of off-axis singularities in free-space vortex transmutation
We experimentally demonstrate the generation of off-axis phase singularities
in a vortex transmutation process induced by the breaking of rotational
symmetry. The process takes place in free space by launching a highly-charged
vortex, owning full rotational symmetry, into a linear thin diffractive element
presenting discrete rotational symmetry. It is shown that off-axis phase
singularities follow straight dark rays bifurcating from the symmetry axis.
This phenomenon may provide new routes towards the spatial control of multiple
phase singularities for applications in atom trapping and particle
manipulation.Comment: 4 pages, 4 figures, to appear in Applied Physics B: Lasers and Optic
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