11,707 research outputs found
Arithmetic properties of the Ramanujan function
We study some arithmetic properties of the Ramanujan function , such
as the largest prime divisor and the number of distinct prime
divisors of for various sequences of . In
particular, we show that \hbox{} for
infinitely many , and \begin{equation*} P(\tau(p)\tau(p^2)\tau(p^3)) >
(1+o(1))\frac{\log\log p\log\log\log p} {\log\log\log\log p} \end{equation*}
for every prime with \hbox{}.Comment: 8 page
Perturbativity Constraints in BSM Models
Phenomenological studies performed for non-supersymmetric extensions of the
Standard Model usually use tree-level parameters as input to define the scalar
sector of the model. This implicitly assumes that a full on-shell calculation
of the scalar sector is possible - and meaningful. However, this doesn't have
to be the case as we show explicitly at the example of the Georgi-Machacek
model. This model comes with an appealing custodial symmetry to explain the
smallness of the parameter. However, the model cannot be renormalised
on-shell without breaking the custodial symmetry. Moreover, we find that it can
often happen that the radiative corrections are so large that any consideration
based on a perturbative expansion appears to be meaningless: counter-terms to
quartic couplings can become much larger than and/or two-loop mass
corrections can become larger than the one-loop ones. Therefore, conditions are
necessary to single out parameter regions which cannot be treated
perturbatively. We propose and discuss different sets of such perturbativity
conditions and show their impact on the parameter space of the Georgi-Machacek
model. Moreover, the proposed conditions are general enough that they can be
applied to other models as well. We also point out that the vacuum stability
constraints in the Georgi-Machacek model, which have so far only been applied
at the tree level, receive crucial radiative corrections. We show that large
regions of the parameter space which feature a stable electroweak vacuum at the
loop level would have been - wrongly - ruled out by the tree-level conditions.Comment: 64 pages, 20 figure
On Kaon production in e+e- and Semi-inclusive DIS reactions
We consider semi-inclusive unpolarized DIS for the production of charged
kaons and the different possibilities to test the conventionally used
assumptions s-\bar=0 and D_d^{K^+-K^-}=0. The considered tests have the
advantage that they do not require any knowledge of the fragmentation
functions. We also show that measurements of both charged and neutral kaons
would allow the determination of the kaon FFs D_q^{K^++K^-} solely from SIDIS
measurements, and discuss the comparison of (D_u-D_d)^{K^+-K^-} obtained
independently in SIDIS and e+e- reactions. All analysis are performed in LO and
NLO in QCD. The feasibility of the tests to HERMES SIDIS data is considered.Comment: 7 pages, NLO analysis for all presented tests and feasibility to
HERMES data adde
Spontaneous Charge Breaking in the NMSSM - Dangerous or not?
We investigate the impact of charge-breaking minima on the vacuum stability
of the NMSSM. We find that, in contrast to Two-Higgs-Doublet Models like the
MSSM, at both tree- and loop-level there exists global charge-breaking minima.
Consequently, many regions of parameter space are rendered metastable, which
otherwise would have been considered stable if these charge-breaking minima
were neglected. However, the inclusion of these new scalar field directions has
little impact on otherwise metastable vacuum configurations.Comment: 7 pages, 4 figure
On two functions arising in the study of the Euler and Carmichael quotients
We investigate two arithmetic functions naturally occurring in the study of
the Euler and Carmichael quotients. The functions are related to the frequency
of vanishing of the Euler and Carmichael quotients. We obtain several results
concerning the relations between these functions as well as their typical and
extreme values
The Ultraviolet Landscape of Two-Higgs Doublet Models
We study the predictions of generic ultraviolet completions of two-Higgs
doublet models. We assume that at the matching scale between the two-Higgs
doublet model and a ultraviolet complete theory -- which can be anywhere
between the TeV and the Planck scale -- arbitrary but perturbative values for
the quartic couplings are present. We evaluate the couplings down from the
matching scale to the weak scale and study the predictions for the scalar mass
spectrum. In particular, we show the importance of radiative corrections which
are essential for both an accurate Higgs mass calculation as well as
determining the stability of the electroweak vacuum. We study the relation
between the mass splitting of the heavy Higgs states and the size of the
quartic couplings at the matching scale, finding that only a small class of
models exhibit a sizeable mass splitting between the heavy scalars at the weak
scale. Moreover, we find a clear correlation between the maximal size of the
couplings and the considered matching scale.Comment: 16 pages, 10 figure
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