# Gamma flip and zero crossings

**DL-05 · Dealer Logic · Core**

**Lesson question:** What makes a Gamma-flip level move?

Original fictional examples; educational writing, not live market data, orders or production approval.

## By the end

- Explain the mechanism in the lesson question.
- Reproduce the worked comparison and recognize its failure case.

**Prerequisites:** DL-01

A Gamma-flip level is a root of a positioning model: a hypothetical spot where estimated net Gamma crosses zero. It is not an exchange-designated support or resistance level. It can change even when the chart does not.

## Understand the mechanism

A spot scan reprices sensitivities while assuming an inventory and a volatility-surface response. Sticky-strike and other surface conventions can produce different results. A book can have multiple roots or no root in the plotted domain.

A shallow crossing is especially sensitive to estimation changes. Reporting one precise line can hide that uncertainty.

## Walk through the process

Inspect the curve around the root, not only the displayed price. Identify which inventory or IV assumptions would shift it. Record its timestamp.

Use the level as a hypothesis for observing a regime transition, not an automatic entry. Acceptance and liquidity still matter.

## Evidence boundary

The arithmetic is original conditional teaching material, not a measurement of current dealer positions. The cited Cboe research is historical product-specific evidence, not a live inventory feed. Model outputs should remain distinguishable from observed market facts.

## A worked example

The fictional model is G(S)=10(S−100) shares per dollar. It equals −20 at 98, zero at 100 and +20 at 102. Adding +30 through a changed inventory assumption gives G(S)=10(S−100)+30, with root 97.

The root moved because an input assumption changed. No claim that spot must travel to 97 follows. The graph shows the original curve.

## Calculation popup: Calculate the hypothetical hedge

```text
10(S−100)+30=0
```

Fictional inputs, explicit units and fixed other factors.

1. 10(S−100)=−30.

2. S=97.

**Result:** Zero at 97 under the changed assumption.

## Graph: Gamma flip and zero crossings—worked comparison

**Horizontal:** Spot (USD)  
**Vertical:** Modeled Gamma (shares/USD)

Fictional data from the written example. The chart organizes the comparison; its shape is not a forecast.

Complete numerical data are embedded in `scripts/dealer-logic/DL-05.js` and displayed as an accessible table in the HTML lesson.

## What would invalidate the reading?

A root is not a price that must repel or attract the market. Multiple crossings and uncertain surface dynamics can defeat a single-line interpretation.

## Check your understanding

### Where is the root of 10(S−100)+30?

**Answer:** 97.

**Why:** Set the model output to zero rather than reading a price target into it.

### What is the critical failure to avoid?

**Answer:** A root is not a price that must repel or attract the market. Multiple crossings and uncertain surface dynamics can defeat a single-line interpretation.

**Why:** Explain this risk before treating the example as a decision rule. A correct calculation does not guarantee a favorable market outcome. **Critical risk check.**

## Takeaway

Return to the question: What makes a Gamma-flip level move? State the observed facts, the assumptions and the failure condition separately.

## References and provenance

The cited references support definitions and conventions. The teaching prose, tickets and numerical scenarios are original; they are not attributed as historical market observations.

- [OIC Greeks](https://www.optionseducation.org/advancedconcepts/understanding-options-greeks)

- [Cboe 0DTE positioning study, May 2025](https://www.cboe.com/insights/posts/0-dt-es-decoded-positioning-trends-and-market-impact)