105 research outputs found
Centre-of-mass separation in quantum mechanics: Implications for the many-body treatment in quantum chemistry and solid state physics
We address the question to what extent the centre-of-mass (COM) separation
can change our view of the many-body problem in quantum chemistry and solid
state physics. It was shown that the many-body treatment based on the
electron-vibrational Hamiltonian is fundamentally inconsistent with the
Born-Handy ansatz so that such a treatment can never respect the COM problem.
Born-Oppenheimer (B-O) approximation reveals some secret: it is a limit case
where the degrees of freedom can be treated in a classical way. Beyond the B-O
approximation they are inseparable in principle. The unique covariant
description of all equations with respect to individual degrees of freedom
leads to new types of interaction: besides the known vibronic (electron-phonon)
one the rotonic (electron-roton) and translonic (electron-translon)
interactions arise. We have proved that due to the COM problem only the
hypervibrations (hyperphonons, i.e. phonons + rotons + translons) have true
physical meaning in molecules and crystals; nevertheless, the use of pure
vibrations (phonons) is justified only in the adiabatic systems. This fact
calls for the total revision of our contemporary knowledge of all non-adiabatic
effects, especially the Jahn-Teller effect and superconductivity. The vibronic
coupling is responsible only for removing of electron (quasi)degeneracies but
for the explanation of symmetry breaking and forming of structure the rotonic
and translonic coupling is necessary.Comment: 39 pages, 11 sections, 3 appendice
The mystery of relationship of mechanics and field in the many-body quantum world
We have revealed three fatal errors incurred from a blind transferring of
quantum field methods into the quantum mechanics. This had tragic consequences
because it produced crippled model Hamiltonians, unfortunately considered
sufficient for a description of solids including superconductors. From there,
of course, Fr\"ohlich derived wrong effective Hamiltonian, from which incorrect
BCS theory arose.
1) Mechanical and field patterns cannot be mixed. Instead of field methods
applied to the mechanical Born-Oppenheimer approximation we have entirely to
avoid it and construct an independent and standalone field pattern. This leads
to a new form of the Bohr's complementarity on the level of composite systems.
2) We have correctly to deal with the center of gravity, which is under the
field pattern "materialized" in the form of new quasipartiles - rotons and
translons. This leads to a new type of relativity of internal and external
degrees of freedom and one-particle way of bypassing degeneracies (gap
formation).
3) The possible symmetry cannot be apriori loaded but has to be aposteriori
obtained as a solution of field equations, formulated in a general form without
translational or any other symmetry. This leads to an utterly revised view of
symmetry breaking in non-adiabatic systems, namely Jahn-Teller effect and
superconductivity. These two phenomena are synonyms and share a unique symmetry
breaking.Comment: 24 pages, 9 sections; remake of abstract, introduction and
conclusion; more physics, less philosoph
Quark mass uncertainties revive KSVZ axion dark matter
The Kaplan-Manohar ambiguity in light quark masses allows for a larger
uncertainty in the ratio of up to down quark masses than naive estimates from
the chiral Lagrangian would indicate. We show that it allows for a relaxation
of experimental bounds on the QCD axion, specifically KSVZ axions in the eV mass range composing 100% of the galactic dark matter halo can evade the
experimental limits placed by the ADMX collaboration.Comment: 9 pages, 5 figure
Isocurvature forecast in the anthropic axion window
We explore the cosmological sensitivity to the amplitude of isocurvature
fluctuations that would be caused by axions in the "anthropic window" where the
axion decay constant f_a >> 10^12 GeV and the initial misalignment angle
Theta_i << 1. In a minimal Lambda-CDM cosmology extended with subdominant
scale-invariant isocurvature fluctuations, existing data constrain the
isocurvature fraction to alpha < 0.09 at 95% C.L. If no signal shows up, Planck
can improve this constraint to 0.042 while an ultimate CMB probe limited only
by cosmic variance in both temperature and E-polarisation can reach 0.017,
about a factor of five better than the current limit. In the parameter space of
f_a and H_I (Hubble parameter during inflation) we identify a small region
where axion detection remains within the reach of realistic cosmological
probes.Comment: 14 pages, 4 figures; v2: matches published versio
An M Theory Solution to the Strong CP Problem and Constraints on the Axiverse
We give an explicit realization of the "String Axiverse" discussed in
Arvanitaki et. al \cite{Arvanitaki:2009fg} by extending our previous results on
moduli stabilization in theory to include axions. We extend the analysis of
\cite{Arvanitaki:2009fg} to allow for high scale inflation that leads to a
moduli dominated pre-BBN Universe. We demonstrate that an axion which solves
the strong-CP problem naturally arises and that both the axion decay constants
and GUT scale can consistently be around GeV with a much
smaller fine tuning than is usually expected. Constraints on the Axiverse from
cosmological observations, namely isocurvature perturbations and tensor modes
are described. Extending work of Fox et. al \cite{Fox:2004kb}, we note that
{\it the observation of tensor modes at Planck will falsify the Axiverse
completely.} Finally we note that Axiverse models whose lightest axion has mass
of order eV and with decay constants of order GeV
require no (anthropic) fine-tuning, though standard unification at
GeV is difficult to accommodate.Comment: 16 pages, 8 figures, v2 References adde
Freeze-In Production of FIMP Dark Matter
We propose an alternate, calculable mechanism of dark matter genesis,
"thermal freeze-in," involving a Feebly Interacting Massive Particle (FIMP)
interacting so feebly with the thermal bath that it never attains thermal
equilibrium. As with the conventional "thermal freeze-out" production
mechanism, the relic abundance reflects a combination of initial thermal
distributions together with particle masses and couplings that can be measured
in the laboratory or astrophysically. The freeze-in yield is IR dominated by
low temperatures near the FIMP mass and is independent of unknown UV physics,
such as the reheat temperature after inflation. Moduli and modulinos of string
theory compactifications that receive mass from weak-scale supersymmetry
breaking provide implementations of the freeze-in mechanism, as do models that
employ Dirac neutrino masses or GUT-scale-suppressed interactions. Experimental
signals of freeze-in and FIMPs can be spectacular, including the production of
new metastable coloured or charged particles at the LHC as well as the
alteration of big bang nucleosynthesis.Comment: 30 pages, 7 figures, PDFLaTex. References adde
String theoretic QCD axions in the light of PLANCK and BICEP2
The QCD axion solving the strong CP problem may originate from antisymmetric
tensor gauge fields in compactified string theory, with a decay constant around
the GUT scale. Such possibility appears to be ruled out now by the detection of
tensor modes by BICEP2 and the PLANCK constraints on isocurvature density
perturbations. A more interesting and still viable possibility is that the
string theoretic QCD axion is charged under an anomalous U(1)_A gauge symmetry.
In such case, the axion decay constant can be much lower than the GUT scale if
moduli are stabilized near the point of vanishing Fayet-Illiopoulos term, and
U(1)_A-charged matter fields get a vacuum value far below the GUT scale due to
a tachyonic SUSY breaking scalar mass. We examine the symmetry breaking pattern
of such models during the inflationary epoch with the Hubble expansion rate
10^{14} GeV, and identify the range of the QCD axion decay constant, as well as
the corresponding relic axion abundance, consistent with known cosmological
constraints. In addition to the case that the PQ symmetry is restored during
inflation, there are other viable scenarios, including that the PQ symmetry is
broken during inflation at high scales around 10^{16}-10^{17} GeV due to a
large Hubble-induced tachyonic scalar mass from the U(1)_A D-term, while the
present axion scale is in the range 10^{9}-5\times 10^{13} GeV, where the
present value larger than 10^{12} GeV requires a fine-tuning of the axion
misalignment angle. We also discuss the implications of our results for the
size of SUSY breaking soft masses.Comment: 29 pages, 1 figure; v3: analysis updated including the full
anharmonic effects, references added, version accepted for publication in
JHE
Dark Radiation and Dark Matter in Large Volume Compactifications
We argue that dark radiation is naturally generated from the decay of the
overall volume modulus in the LARGE volume scenario. We consider both
sequestered and non-sequestered cases, and find that the axionic superpartner
of the modulus is produced by the modulus decay and it can account for the dark
radiation suggested by observations, while the modulus decay through the
Giudice-Masiero term gives the dominant contribution to the total decay rate.
In the sequestered case, the lightest supersymmetric particles produced by the
modulus decay can naturally account for the observed dark matter density. In
the non-sequestered case, on the other hand, the supersymmetric particles are
not produced by the modulus decay, since the soft masses are of order the heavy
gravitino mass. The QCD axion will then be a plausible dark matter candidate.Comment: 27 pages, 4 figures; version 3: version published in JHE
A Transfer Matrix Method for Resonances in Randall-Sundrum Models
In this paper we discuss in detail a numerical method to study resonances in
membranes generated by domain walls in Randall-Sundrum-like scenarios. It is
based on similar works to understand the quantum mechanics of electrons subject
to the potential barriers that exist in heterostructures in semiconductors.
This method was used recently to study resonances of a three form field and
lately generalized to arbitrary forms. We apply it to a lot of important
models, namely those that contain the Gauge, Gravity and Spinor fields. In many
cases we find a rich structure of resonances which depends on the parameters
involved.Comment: 25 pages, 17 figure
D-brane potentials in the warped resolved conifold and natural inflation
In this paper we obtain a model of Natural Inflation from string theory with
a Planckian decay constant. We investigate D-brane dynamics in the background
of the warped resolved conifold (WRC) throat approximation of Type IIB string
compactifications on Calabi-Yau manifolds. When we glue the throat to a compact
bulk Calabi-Yau, we generate a D-brane potential which is a solution to the
Laplace equation on the resolved conifold. We can exactly solve this equation,
including dependence on the angular coordinates. The solutions are valid down
to the tip of the resolved conifold, which is not the case for the more
commonly used deformed conifold. This allows us to exploit the effect of the
warping, which is strongest at the tip. We inflate near the tip using an
angular coordinate of a D5-brane in the WRC which has a discrete shift
symmetry, and feels a cosine potential, giving us a model of Natural Inflation,
from which it is possible to get a Planckian decay constant whilst maintaining
control over the backreaction. This is because the decay constant for a wrapped
brane contains powers of the warp factor, and so can be made large, while the
wrapping parameter can be kept small enough so that backreaction is under
control.Comment: 41 pages, 3 appendices, 1 figure, PDFLaTex; various clarifications
added along with a new appendix on b-axions and wrapped D5 branes;version
matches the one published in JHE
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